U.S. patent application number 13/339319 was filed with the patent office on 2012-04-26 for polymer composition prepared from acrylic polymer grafted with a functionalized block copolymers.
This patent application is currently assigned to KRATON POLYMERS U.S. LLC. Invention is credited to Donn Anthony Dubois, Richard Gelles, David John St. Clair.
Application Number | 20120101231 13/339319 |
Document ID | / |
Family ID | 40523827 |
Filed Date | 2012-04-26 |
United States Patent
Application |
20120101231 |
Kind Code |
A1 |
Gelles; Richard ; et
al. |
April 26, 2012 |
Polymer Composition prepared from acrylic polymer grafted with a
functionalized block copolymers
Abstract
The present invention relates to various end use applications
prepared from certain block copolymers. The block copolymers
include one or more A or A' blocks or B blocks plus one or more
terminal M blocks. Each A and A' is a block or segment comprising
predominantly a polymerized alkenyl aromatic compound, each B is a
block or segment comprising predominantly a polymerized conjugated
alkadiene, and each M is a six membered anhydride ring and/or acid
group. The anhydride rings are prepared by thermally decomposing
adjacent units of (1-methyl-1-alkyl)alkyl acrylic esters such as
t-butylmethylacrylate. A wide variety of polymers are disclosed
having the stable anhydride rings in the polymer backbone. The
invention relates specifically to various end uses prepared from
the reaction product of such block copolymers with various reactive
resins, reactive monomers and metal derivatives.
Inventors: |
Gelles; Richard; (Houston,
TX) ; Dubois; Donn Anthony; (Houston, TX) ;
St. Clair; David John; (Houston, TX) |
Assignee: |
KRATON POLYMERS U.S. LLC
Houston
TX
|
Family ID: |
40523827 |
Appl. No.: |
13/339319 |
Filed: |
December 28, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12248184 |
Oct 9, 2008 |
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13339319 |
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60978484 |
Oct 9, 2007 |
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Current U.S.
Class: |
525/94 |
Current CPC
Class: |
C08F 8/00 20130101; C08F
8/00 20130101; C08F 8/48 20130101; C09J 163/00 20130101; C09J
153/005 20130101; C08F 8/04 20130101; C08L 2666/04 20130101; C08L
75/04 20130101; C08F 8/14 20130101; C08L 9/06 20130101; C08L 53/025
20130101; C09J 163/00 20130101; C08F 297/04 20130101; C08F 297/026
20130101; C08F 297/04 20130101; C08L 2666/04 20130101; C08F 297/026
20130101; C08L 2666/20 20130101; C08F 297/026 20130101; C08F 297/04
20130101; C08F 297/026 20130101; C08F 8/48 20130101; C08F 8/48
20130101; C08F 8/04 20130101; C08F 8/14 20130101; C08L 53/025
20130101; C08F 8/00 20130101; C08F 8/04 20130101 |
Class at
Publication: |
525/94 |
International
Class: |
C08F 287/00 20060101
C08F287/00 |
Claims
1-14. (canceled)
15. An acrylic composition comprising an acrylic copolymer reacted
with a block copolymer, wherein said acrylic copolymer has a glass
transition temperature below 0.degree. C. and contains at least one
comonomer unit possessing a pendant reactive group capable of
reacting with said block copolymer and wherein said block copolymer
comprises at least one block of a polymerized conjugated diene
and/or a polymerized alkenyl aromatic and at least one end block
comprising a six membered anhydride ring and/or acid.
16. The acrylic composition of claim 15 wherein said acrylic
composition is further reacted with an acrylic monomer selected
from the group consisting of methyl acrylate, ethyl acrylate,
isobutyl methacrylate, methyl methacrylate and mixtures
thereof.
17. The acrylic composition of claim 16 wherein said acrylic
copolymer is selected from the group consisting of (meth)acrylic
ester/hydroxy (meth) alkyl ester copolymers, (meth)acrylic
ester/glycidyl (meth) alkyl ester copolymers, (meth)acrylic
ester/(meth)acrylic acid copolymers and (meth)acrylic
ester/acrylamide copolymers.
18. The acrylic composition according to claim 15 wherein said base
block copolymer prior to heating to form the anhydride rings and
reaction with said reactive monomer or reactive resin or metal
derivative comprises at least one block selected from the group
consisting of (a) a block of at least 80% by mole polymerized
styrene, and (b) a block of polymerized, hydrogenated butadiene
having at least some 1,2-enchainments, or a block of polymerized,
hydrogenated isoprene, or a block of polymerized, hydrogenated
isoprene and butadiene and further comprises (c) a terminal block
of polymerized t-butyl methacrylate polymerized through the
ethylenic unsaturation thereof, wherein the block copolymer has the
formula A-M, B-M, B-A-M, A-B-M or A-B-A'-M wherein A and A' are
blocks of the polymerized aromatic styrene, B is the block of the
hydrogenated, polymerized butadiene, isoprene or mixtures of
butadiene and isoprene, and M is the terminal block of the
polymerized t-butyl methacrylate, and wherein each block of the
polymerized styrene has a number average molecular weight from
about 2,000 to about 50,000, the block of the hydrogenated,
polymerized diene has a number average molecular weight from about
20,000 to about 500,000, and the terminal M block has a number
average molecular weight of 500 to about 100,000.
19. The acrylic composition of claim 15, wherein said acrylic
copolymer comprises (a) at least one alkyl acrylate monomer
containing from about 4 to about 18 carbon atoms in the alkyl
group, and (b) at least one monomer selected from the group
consisting of methyl acrylate, ethyl acrylate, isobutyl
methacrylate, vinyl acetate, methyl methacrylate, acrylonitrile,
styrene, and mixtures thereof, and wherein said functionalized
block copolymer comprises the reaction product of (i) a block
copolymer comprising at least one block of a polymerized conjugated
diene or a polymerized alkenyl aromatic and at least one end block
comprising a six membered anhydride ring and/or acid and (ii) at
least one reactive monomer.
20. The acrylic composition of claim 19 wherein said reactive
monomer is selected from the group consisting of hydroxy functional
monomers, carboxy functional monomers, glycidyl functional
monomers, acrylamide functional monomers, amine functional
monomers, epoxy functional monomers, isocyanate functional monomers
and mixtures thereof
21. The acrylic composition of claim 20 wherein said acrylate
monomer is selected from the group consisting of 2-ethyl hexyl
acrylate, methyl acrylate, and hydroxyethyl acrylate.
22. The acrylic composition of claim 21 wherein said acrylic
copolymer is crosslinked using a titanium crosslinking agent.
23-25. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of U.S.
provisional patent application Ser. No. 60/978,484, filed Oct. 9,
2007, entitled End Use Applications Prepared from Certain Block
Copolymers.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to various end use applications
prepared from certain block copolymers having anhydride and/or acid
groups. The invention relates specifically to various end uses
prepared from the reaction product of such block copolymers with
various reactive resins, reactive monomers and metal derivatives.
In part, the present invention relates to formulations comprising
an acrylic polymer grafted with a particular functionalized block
copolymer prepared from certain block copolymers having anhydride
and/or acid groups.
[0004] 2. Background of the Art
[0005] Elastomeric polymers, both homopolymers and polymers of more
than one monomer, are well known in the art. A particularly useful
class of synthetic elastomers is the class of thermoplastic
elastomers which demonstrates elastomeric properties at ambient
temperatures but which is processable at somewhat elevated
temperatures by methods more conventionally employed for
non-elastomeric thermoplastics. Such thermoplastic elastomers are
illustrated by a number of types of block polymers including, for
example, block polymers of alkenyl aromatic compounds and
conjugated alkadiene. Block polymers of styrene and butadiene are
illustrative. This particular type of block polymer is well known
in the art and includes KRATON.RTM. block copolymers.
[0006] The properties of block polymers, even containing the same
or similar monomers, will vary considerably with the arrangement of
the monomeric blocks within the block polymer and with the relative
molecular weight of each block. It is also known that certain of
the properties such as resistance to oxidation of this class of
block polymers are improved by the selective hydrogenation of some
or all of the carbon-carbon unsaturation in the polyalkadiene or
aliphatic portion of the molecule and, on occasion, by the
hydrogenation of substantially all the carbon-carbon unsaturation
including that unsaturation in the poly(alkenyl aromatic compound)
or aromatic portion of the molecule. A number of the selectively
hydrogenated block polymers are also well known and commercial,
such as KRATON.RTM. G block copolymers.
[0007] An alternate method of modifying selected properties of the
block polymers is to provide polarity or functionality within the
block polymer as by introducing functional groups as substituents
within the molecule or by providing one or more additional blocks
within the polymeric structure which are polar in character. Such
polymers included maleated block copolymers, such as KRATON.RTM. FG
block copolymers.
[0008] The problem with many of the prior art block copolymers is
that they are not polar, reactive, nor hydrophilic. U.S. Pat. No.
5,218,053 discloses a novel polymer that contains anhydride rings.
The anhydride rings are prepared by thermally decomposing adjacent
units of (1-methyl-1-alkyl)alkyl esters such as in a
poly(t-butylmethylacrylate) block. This thermal reaction forms
predominately a six-membered glutaric anhydride ring in addition to
some carboxylic acid groups. In the case of low reaction
conversion, unreacted ester groups may also be present. In
addition, the anhydride rings will form at least some carboxylic
acid groups upon contact with water. Accordingly, the resulting
polymer may contain ester, anhydride and acid groups. A number of
polymers were disclosed in the '053 patent having the anhydride
rings in the polymer backbone.
Adhesives, Sealants and Coatings
[0009] Such anhydride containing block copolymers have been used to
make various adhesives, sealants and coatings as disclosed in U.S.
Pat. No. 5,403,658 and US SIR H1251. U.S. Pat. No. 5,403,658
discloses adhesives with aggressive tack (pressure sensitive
adhesives) which adhere well to Kraft paper. US SIR H1251 discloses
hot melt adhesives which adhere well to polar substrates including
steel and glass. Both patents disclose hydrogenated anhydride
containing block copolymers. However the prior art does not
disclose contact adhesives and coatings and does not disclose the
reaction product of anhydride containing block copolymers with
reactive resins, reactive monomers and reactive metal
derivatives.
Acrylic Pressure Sensitive Adhesives
[0010] Typical acrylic pressure sensitive adhesive formulations are
copolymers of alkyl ester monomers, a functional monomer such as
acrylic acid, and may be crosslinked using, for example, aluminum
chelates. These adhesives are generally deficient in adhesion to
low energy surfaces. While adhesives may be tackified with rosin
esters to improve low surface energy adhesion, tackification
results in loss of heat resistance and poor aging properties. Even
though good aging properties are compromised, tackified acrylic
dispersions are sufficient for some applications, e.g. most paper
label uses and, indeed, have become the dominant paper label
technology. These tackified acrylic adhesives, however, do not have
sufficient resistance to degradation for most graphics and
industrial tape applications in which acrylic solutions are
conventionally used.
[0011] Rubber-resin formulations are often used to adhere to
polyolefins and other low energy substrates. Typical compositions
are natural rubber or styrene block copolymers tackified with rosin
esters. These formulations provide excellent tack and cohesive
strength but discolor and lose tack on aging due to oxidative and
UV light induced degradation. Formulations of fully hydrogenated
rubbers and resins, besides being more costly, generally do not
have the required adhesive performance.
[0012] U.S. Pat. No. 5,625,005 discloses rubber-acrylic pressure
sensitive adhesives described as having good UV resistance and
aging characteristics along with high adhesion to non-polar
surfaces. U.S. Pat. Nos. 6,642,298 and 6,670,417 disclose improved
acrylic pressure sensitive adhesives containing an acrylic polymer
grafted with a hydrogenated rubber macromer. Despite these advances
in the art, there remains a need for improved polymer compositions
which can be used to prepare pressure sensitive adhesives having
sufficient adhesion and chemical resistance properties for
applications such as industrial tapes and transfer films, and
exterior graphics applications on low energy, difficult to adhere
to surfaces.
Structural Acrylic Adhesives
[0013] Structural acrylic adhesives are well known for bonding a
wide variety of substrates. They are used as an alternative to
mechanical joining methods for a number of reasons including cost,
aesthetics, and noise reduction. They typically are made via a
mixture of a methacrylate ester monomer, a polymerization catalyst
and several other ingredients. Structural acrylic adhesives have
several potential drawbacks including poor flexibility and poor
adhesion to non-polar surfaces. U.S. Pat. No. 6,989,416 discloses
methacrylate structural acrylic adhesives that include elastomeric
materials including block copolymers of styrene, and isoprene or
butadiene. The elastomeric materials improve the impact strength
and flexibility of the adhesive. These block copolymers are used
because they can be mixed with methacrylate monomers to create
uniform mixtures, and can graft to the acrylic polymer via free
radical grafting. However block copolymers of isoprene and
butadiene have the drawback of poor UV resistance and aging
compared to acrylic polymers.
Acrylic Sealants and Coatings
[0014] Various sealant compositions have been disclosed in the
prior art. The basic patent for sealants comprising styrenic block
copolymers is Harlan, U.S. Pat. No. 3,239,478, which shows
combinations of styrene-diene block copolymers with tackifying
resins and the like to produce a wide spectrum of sealants and
adhesives. Sealants made with non-hydrogenated styrene-diene block
copolymers, such as those disclosed in U.S. Pat. No. 4,101,482 lack
the necessary oxidative and UV stability. Sealants based on
commercially available hydrogenated styrene-diene block copolymers,
such as those disclosed in U.S. Pat. No. 4,113,914, also have
certain shortcomings. These sealants have good hardness,
temperature resistance and UV resistance, but the failure mechanism
is adhesive failure, which failure mechanism is not acceptable in
sealants. In addition, the melt viscosity is too high for many
commercial operations. A novel sealant composition is disclosed in
U.S. Pat. No. 4,296,008 that not only gives better tack and lower
melt viscosity (especially in formulations containing no
plasticizers), but also results in cohesive as opposed to adhesive
failure. However, sealants comprising styrenic block copolymers
often contain solvent to lower viscosity. The general trend is away
from solvent based sealants because of environmental concerns.
While sealants based on acrylic lattices do not match silicone and
urethane sealants in performance, they are less expensive and are
used in over the counter and do it yourself construction markets.
Typically hard acrylic esters like methyl methacrylate, vinyl
acetate, and methyl acrylate are used in combination with monomers
which give flexibility including butyl acrylate and 2-ethylhexyl
acrylate. In general, acrylic adhesives, sealants and coatings
exhibit excellent ultraviolet (uv) stability and resistance to
thermal degradation. However, acrylic based adhesives sealants and
coatings in general suffer from poor adhesion to low energy and low
polarity surfaces and rigid acrylics suffer from poor flexibility
and impact strength.
Radiation Cured Adhesives, Sealants, Coatings and Printing
Plates
[0015] Monoalkenyl arene/conjugated diene block copolymers are
widely used in pressure sensitive adhesives (PSA). PSA based on
these polymers have high strength and elasticity at ambient
temperatures, making them well suited for use in many general
purpose applications, and in packaging and cloth tapes. The high
strength and elasticity of these PSAs is due to the well known
microphase separated network structure in which the monoalkenyl
arene endblocks, phase separate to form domains serving to
physically crosslink the rubbery midblock phase. However, at
temperatures approaching the glass transition temperature of the
endblocks or in the presence of an appropriate solvent, the domains
soften, releasing the physical crosslinks and the PSA loses its
strength and elasticity. Therefore, PSA based on a block copolymer
are unsuitable for use in high temperature or solvent resistant
tapes, such as automobile masking tapes. The only method of
maintaining high cohesive strength in a PSA based on a block
copolymer at high temperature or in the presence of solvent is to
chemically crosslink the polymer in order that the polymer no
longer depends on the physical crosslinks for its strength.
[0016] Radiation cured adhesives, sealants and coatings are well
known in the art and can be divided into ultraviolet (UV), visible
light curable and electron beam curable formulations. Examples of
the prior art include U.S. Pat. No. 5,777,039 U.S. Pat. No.
4,556,464 and U.S. Pat. No. 4,133,731. In general, adhesives,
sealants and coatings are cured (crosslinked) to improve mechanical
properties at elevated temperature like cohesive strength, shear
strength and creep resistance. Curing by radiation requires
monomers and polymers with functional groups. Monomers and polymers
with acrylic functionality are often used. Monomers and polymers
with epoxy functionality can be used for cationic curing, and
monomers and polymers with thiol functionality may also be used for
radiation cure. However, the polymers of the prior art continue to
have certain shortcomings, including the lack of acceptable
resistance to aging and UV light.
[0017] What has now been found is that the novel block copolymer
compositions of the present invention have surprising property
advantages, and show promising utility in a variety of end-use
applications. The present invention overcomes several limitations
in the prior art, for example permitting the preparation of contact
adhesives with improved cohesive strength, and coatings with
improved toughness or flexibility. The present invention is an
improvement over past acrylic adhesives, sealants and coatings, and
the novel formulations claimed here exhibit excellent adhesion to
low energy and low polarity surfaces.
SUMMARY OF THE INVENTION
[0018] As used herein, the term "hybrid block copolymer" refers to
a block copolymer composition comprising (1) at least one block of
a polymerized conjugated diene (or hydrogenated version) or a
polymerized alkenyl aromatic and at least one end block comprising
a repeat unit of a six membered anhydride ring (or a reaction
product of a six membered anhydride ring with water to form the
corresponding carboxylic acid) and (2) a reactive monomer or
reactive resin or reactive metal derivative that will react with
the anhydride and/or acid groups. Furthermore, the base block
copolymer can also contain unreacted alkyl methacrylate repeats in
addition to anhydride or the open-ring carboxylic acid. In a
preferred embodiment, the hybrid block copolymers are prepared by a
process comprising the steps of: [0019] (a) anionically
polymerizing a conjugated alkadiene or an alkenyl aromatic compound
to form living polymer molecules; [0020] (b) anionically
polymerizing a methacrylic or acrylic monomer bearing a
(1-methyl-1-alkyl)alkyl ester to form adjacent units of the ester
on the living polymer molecules; [0021] (c) recovering the polymer
molecules; [0022] (d) heating the polymer molecules to convert at
least some of the adjacent ester groups to anhydride rings (the
process of (c) may provide sufficient heat to convert the ester
groups to anhydride); and [0023] (e) reacting the resulting polymer
with a reactive monomer or resin or metal derivative.
[0024] As used herein, the term "pressure-sensitive adhesive"
refers to a viscoelastic material which adheres instantaneously to
most substrates with the application of slight pressure and remains
permanently tacky. A polymer is a pressure-sensitive adhesive
within the meaning of the term as used herein if it has the
properties of a pressure-sensitive adhesive per se or functions as
a pressure-sensitive adhesive by admixture with tackifying resins,
plasticizers or other additives. As used herein the term
"structural adhesive" refers to a bonding agent used to transfer
loads between adherents. Structural adhesives can be rigid or
flexible and typically have high strength, durability and heat
resistance. The term "sealant" refers to a material that fills the
gap between two substrates and gives a tight and perfect closure
against the passage of a liquid such as water or a gas or vapor
such as water vapor. The term "coating" refers to a material that
is spread over and adheres to a substrate and provides some
property advantage to the substrate.
[0025] Preferably the reactive resins are selected from the group
consisting of phenolic resins, amino resins, epoxy resins and
polyurethanes. Preferably the reactive monomers are selected from
the group consisting of hydroxy functional monomers, carboxy
functional monomers, glycidyl functional monomers, acrylamide
functional monomers, amine functional monomers, epoxy functional
monomers, isocyanate functional monomers and mixtures thereof.
Preferably the metal derivatives are selected from the group
consisting of calcium oxide, magnesium oxide, zinc oxide, calcium
stearate, zinc stearate, zinc acetate and mixtures thereof.
[0026] The present invention provides adhesive, sealant and coating
formulations prepared from certain acrylic polymers or acrylic
monomers and with a particular functionalized block copolymer
prepared from certain block copolymers having anhydride and/or acid
groups.
[0027] These various formulations are novel, and result in products
having unexpected property advantages. For example, the resulting
adhesive formulations have outstanding coating characteristics,
adhesion to a wide variety of substrates, including low energy
surfaces, while maintaining these performance properties at higher
temperatures in their dried state.
[0028] The present invention claims various new compositions of
matter, including: [0029] (1) a functionalized block copolymer
comprising the reaction product of (i) a block copolymer comprising
at least one block of a polymerized conjugated diene and/or a
polymerized alkenyl aromatic and at least one end block comprising
a six membered anhydride ring and/or the corresponding carboxylic
acid formed from the reaction of this ring and water and (ii) at
least one reactive monomer. In a preferred embodiment the reactive
monomer is selected from hydroxy functional monomers, carboxy
functional monomers, glycidyl functional monomers, acrylamide
functional monomers, amine functional monomers, epoxy functional
monomers, isocyanate functional monomers and mixtures thereof;
[0030] (2) a functionalized block copolymer comprising the reaction
product of (i) a block copolymer comprising at least one block of a
polymerized conjugated diene and/or a polymerized alkenyl aromatic
and at least one end block comprising a six membered anhydride ring
and/or the corresponding carboxylic acid formed from the reaction
of this ring and water and (ii) at least one acrylic copolymer
containing at least one pendant reactive group; [0031] (3) a
functionalized block copolymer comprising the reaction product of
(i) a block copolymer comprising at least one block of a
polymerized conjugated diene and/or a polymerized alkenyl aromatic
and at least one end block comprising a six membered anhydride ring
and/or the corresponding carboxylic acid formed from the reaction
of this ring and water and (ii) at least one reactive resin
selected from the group consisting of phenolic resins, amino
resins, polyurethanes and epoxy resins; and [0032] (4) an acrylic
composition comprising an acrylic polymer reacted with a block
copolymer, wherein said acrylic copolymer has a glass transition
temperature below 0.degree. C. and contains at least one vinylic
comonomer unit possessing a pendant reactive group capable of
reacting with said block copolymer and wherein said block copolymer
comprises at least one block of a polymerized conjugated diene
and/or a polymerized alkenyl aromatic and at least one end block
comprising a six membered anhydride ring and/or acid.
[0033] In a further preferred embodiment, the hybrid block
copolymers prior to heating to form the anhydride rings and
reaction with the functional monomer comprise (a) a block of
polymerized styrene, (b) a block of polymerized, hydrogenated
butadiene having at least some 1,2-enchainments, or a block of
polymerized, hydrogenated isoprene, or a block of polymerized,
hydrogenated isoprene and butadiene and (c) a terminal block of
polymerized t-butyl methacrylate polymerized through the ethylenic
unsaturation thereof, wherein the block copolymer has the
formula
A-M, B-M, B-A-M, A-B-M or A-B-A'-M
wherein A and A' are blocks of the polymerized aromatic styrene, B
is the block of the hydrogenated, polymerized butadiene, isoprene
or mixtures of butadiene and isoprene, and M is the terminal block
of the polymerized t-butyl methacrylate, and wherein each block of
the polymerized styrene has a number average molecular weight from
about 2,000 to about 50,000, the block of the hydrogenated,
polymerized diene has a number average molecular weight from about
20,000 to about 500,000, and the terminal M block has a number
average molecular weight of 500 to about 100,000.
[0034] In one aspect of the present invention we have discovered a
novel contact adhesive composition, said contact adhesive
comprising at least one block copolymer, a reactive resin, and a
solvent. In a preferred embodiment the contact adhesive comprises
100 parts by weight of at least one base block copolymer, 20 to 500
parts by weight of a heat reactive phenolic resin, 1 to 10 parts by
weight of a metal oxide such as magnesium oxide, and a solvent,
such as toluene or a solvent blend of toluene, hexane or heptane
and acetone.
[0035] In another aspect of the present invention we have
discovered a novel solvent based adhesive composition comprising
100 parts by weight of at least one hybrid block copolymer, 25 to
300 parts by weight of at least one tackifying resin, and 0 to 200
parts by weight of a plasticizer and a solvent or solvent
mixture.
[0036] In another aspect of the present invention we have
discovered a novel composition comprising the hybrid block
copolymers of the present invention prepared by reaction of the
base polymer with monomers and resins containing epoxy, isocyanate
and amine functional groups. These compositions include novel epoxy
compositions, ambient cure urethane compositions and bake cure
compositions.
[0037] One aspect of the invention relates to an acrylic
composition comprising (a) an acrylic polymer containing pendant
reactive groups and/or (b) an acrylic monomer containing pendant
reactive groups, said monomer or polymer being reacted with a block
copolymer wherein said block copolymer comprises at least one block
of a polymerized conjugated diene and/or a polymerized alkenyl
aromatic and at least one end block comprising a six membered
anhydride ring and/or acid. Preferred acrylic polymers have a glass
transition temperature below 0.degree. C., containing at least one
comonomer unit possessing a pendant reactive group and preferred
acrylic monomers include methyl acrylate, ethyl acrylate, isobutyl
methacrylate, and methyl methacrylate.
[0038] Another aspect of the invention is directed to a
pressure-sensitive adhesive comprising an acrylic polymer
copolymerized with a block copolymer, wherein said acrylic polymer
comprises: (a) at least one alkyl acrylate monomer containing from
about 4 to about 18 carbon atoms in the alkyl group, (b) at least
one monomer selected from the group consisting of methyl acrylate,
ethyl acrylate, isobutyl methacrylate, vinyl acetate, methyl
methacrylate, acrylonitrile, styrene, and mixtures thereof; and (c)
at least one reactive monomer selected from hydroxy functional
monomers, carboxy functional monomers, glycidyl functional
monomers, acrylamide functional monomers, amine functional
monomers, epoxy functional monomers, isocyanate functional monomers
and mixtures thereof, and wherein said block copolymer comprises at
least one block of a polymerized conjugated diene and/or a
polymerized alkenyl aromatic and at least one end block comprising
a six membered anhydride ring and/or acid.
[0039] Another aspect of the invention is directed to a
pressure-sensitive adhesive comprising an acrylic polymer
copolymerized with a functionalized block copolymer, wherein said
acrylic polymer comprises: (a) at least one alkyl acrylate monomer
containing from about 4 to about 18 carbon atoms in the alkyl
group, and (b) at least one monomer selected from the group
consisting of methyl acrylate, ethyl acrylate, isobutyl
methacrylate, vinyl acetate, methyl methacrylate, acrylonitrile,
styrene, and mixtures thereof, and wherein said functionalized
block copolymer comprises the reaction product of (i) a block
copolymer comprising at least one block of a polymerized conjugated
diene and/or a polymerized alkenyl aromatic and at least one end
block comprising a six membered anhydride ring and/or acid and (ii)
at least one reactive monomer selected from hydroxy functional
monomers, carboxy functional monomers, glycidyl functional
monomers, acrylamide functional monomers, amine functional
monomers, epoxy functional monomers, isocyanate functional monomers
and mixtures thereof
[0040] Still another aspect of the invention is directed to a
process of making a pressure-sensitive adhesive comprising reacting
(a) at least one alkyl acrylate monomer containing from about 4 to
about 18 carbon atoms in the alkyl group with (b) at least one
monomer selected from the group consisting of methyl acrylate,
ethyl acrylate, isobutyl methacrylate, vinyl acetate, methyl
methacrylate, acrylonitrile, styrene, and mixtures thereof and
mixtures thereof, and with (c) a functionalized block copolymer,
wherein said functionalized block copolymer comprises the reaction
product of (i) a block copolymer comprising at least one block of a
polymerized conjugated diene or a polymerized alkenyl aromatic and
at least one end block comprising a six membered anhydride ring
and/or acid and (ii) at least one reactive monomer selected from
hydroxy functional monomers, carboxy functional monomers, glycidyl
functional monomers, acrylamide functional monomers, amine
functional monomers, epoxy functional monomers and mixtures
thereof.
[0041] Yet another aspect of the invention is directed to adhesive
articles, e.g., industrial tapes, transfer films, and the like,
comprising a pressure sensitive adhesive hybrid polymer. In one
particularly preferred embodiment, the hybrid polymer comprises an
acrylic polymer copolymerized with a functionalized block
copolymer, wherein said acrylic polymer comprises: (a) at least one
alkyl acrylate monomer containing from about 4 to about 18 carbon
atoms in the alkyl group, and (b) at least one monomer selected
from the group consisting of methyl acrylate, ethyl acrylate,
isobutyl methacrylate, vinyl acetate and mixtures thereof, and
wherein said functionalized block copolymer comprises the reaction
product of (i) a block copolymer comprising at least one block of a
polymerized conjugated diene or a polymerized alkenyl aromatic and
at least one end block comprising a six membered anhydride ring
and/or acid and (ii) at least one reactive monomer selected from
hydroxy functional monomers, carboxy functional monomers, glycidyl
functional monomers, acrylamide functional monomers, amine
functional monomers, epoxy functional monomers and mixtures
thereof
[0042] The largest consumption of acrylic adhesives and sealants is
with acrylic polymers prepared by emulsion polymerization. Emulsion
polymerized acrylics give acrylic polymer, adhesive, sealant and
coating manufacturing processes and end user application processes
which are low cost and environmentally friendly. The present
invention describes a hybrid rubber-acrylic polymer which can be
prepared in solution, in a mixture of monomers, in an emulsion or
suspension of monomers, or in the melt.
[0043] The block copolymer can be reacted with the acrylic monomers
during copolymerization (a "macromer" process), or alternatively,
the block copolymer can be reacted with a polymerized acrylic
polymer by reaction between the functional monomers in the acrylic
polymer and the end block comprising a six membered anhydride ring
or the acid formed from the reaction of this ring and water (the
post polymerization reaction process). These two processes are
shown schematically below:
##STR00001##
[0044] The present invention describes acrylic polymers grafted
with the block copolymers described above. Thus the hydrogenated
block copolymer segments, in particular the rubber phase, impart
improved adhesion to low energy surfaces, as in the prior art, but
give improved cohesive strength and flow resistance at elevated
temperature compared to the prior art in the case of pressure
sensitive adhesives, and gives improved uv weathering and heat
aging stability compared to the prior art in the case of structural
adhesives.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0045] The key component of the present invention is the hybrid
block copolymer composition as defined above. The process for
making the starting base block copolymer is described and claimed
in the U.S. Pat. No. 5,218,053, which disclosure is herewith
incorporated by reference.
[0046] The base polymers of the present invention prior to
formation of the anhydride rings are exemplified by the following
structures:
A-M I
B-M II
B-M-B III
M-B-M IV
(B-M-).sub.y-X V
(M-B-).sub.y-Z VI
A-B-M VII
B-A-M VIII
A-B-A'-M IX
M-A-B-A'-M X
(A-B-M-).sub.y-X XI
(M-A-B-).sub.y-Z XII
(M-B-A-).sub.y-Z XIII
(A-M-).sub.y-X XIV
(M-A-).sub.y-Z XV
wherein each A and A' is a block or segment comprising
predominantly a polymerized alkenyl aromatic compound, each B is a
block or segment comprising predominantly a polymerized conjugated
alkadiene, each M is a segment or block comprising at least two
adjacent units of a polymerized (1-methyl-1-alkyl)alkyl ester, y is
an integer representing multiple arms in a star configuration, X is
the residue of a polyfunctional coupling agent, and Z is a
crosslinked core of a polyfunctional coupling agent or a
polyfunctional polymerization initiator.
[0047] The alkenyl aromatic compound employed as each A and A'
block or segment in some of the above structures is a hydrocarbon
compound of up to 18 carbon atoms having an alkenyl group of up to
6 carbon atoms attached to a ring carbon atom of an aromatic ring
system of up to 2 aromatic rings. Such alkenyl aromatic compounds
are illustrated by styrene, 2-butenylnaphthalene,
4-t-butoxystyrene, 3-isopropenylbiphenyl, and
isopropenylnaphthalene. The preferred alkenyl aromatic compounds
have an alkenyl group of up to 3 carbon atoms attached to a benzene
ring as exemplified by styrene and styrene homologs such as
styrene, .alpha.-methylstyrene, p-methylstyrene, and
.alpha.,4-dimethylstyrene. Also included are monomers such as
1,1-diphenylethylene monomer, 1,2-diphenylethylene monomer, and
mixtures thereof. Styrene and .alpha.-methylstyrene are
particularly preferred alkenyl aromatic compounds, especially
styrene.
[0048] Each A and A' block or segment of the polymers is preferably
at least 80% by weight polymerized alkenyl aromatic compound and is
most preferably a homopolymer. Each B block or segment in the
structures of Formula II-XIII preferably comprises at least 90% by
weight of the polymerized conjugated alkadiene. Most preferably,
the B segments or blocks are homopolymers or copolymers of one or
more conjugated alkadienes. The conjugated alkadienes preferably
have up to 8 carbon atoms. Illustrative of such conjugated
alkadienes are 1,3-butadiene (butadiene), 2-methyl-1,3-butadiene
(isoprene), 1,3-pentadiene (piperylene), 1,3-octadiene, and
2-methyl-1,3-pentadiene. Preferred conjugated alkadienes are
butadiene and isoprene, particularly butadiene. Within the
preferred polyalkadiene blocks or segments of the polymers of
Formula II-XIII, the percentage of units produced by 1,4
polymerization is at least about 5% and preferably at least about
20%. In addition, copolymers of conjugated dienes and alkenyl
aromatics are also included, where the structure may be a random
copolymer, a tapered copolymer or a controlled distribution block
copolymer. Controlled distribution block copolymers are disclosed
in U.S. Pat. No. 7,169,848, which disclosure is herein incorporated
by reference.
[0049] Each M is preferably a methacrylate block or segment
comprising at least two adjacent units of a polymerized
(1-methyl-1-alkyl)alkyl methacrylate. Homopolymeric M segments or
blocks of (1-methyl-1-alkyl)alkyl methacrylates are most
preferred.
[0050] The alkyl esters have the following structure:
Monomer:
##STR00002##
[0051] Anhydride Ring:
##STR00003##
[0052] Reaction of ester to anhydride
##STR00004##
wherein R.sub.1 is hydrogen or an alkyl or aromatic group
comprising from 1 to 10 carbon atoms and R.sub.2 is an alkyl group
comprising from 1 to 10 carbon atoms.
[0053] Adjacent (1-methyl-1-alkyl)alkyl ester groups thermally
convert to stable anhydride rings having six members after
reaction.
[0054] Examples of the (1-methyl-1-alkyl) alkyl esters include:
[0055] 1,1-dimethylethylacrylate (t-butylacrylate), [0056]
1,1-dimethylpropylacrylate (t-pentylacrylate), [0057]
1,1-dimethylethyl-.alpha.-propylacrylate, [0058]
1-methyl-1-ethylpropyl-.alpha.-butylacrylate, [0059]
1,1-dimethylbutyl-.alpha.-phenylacrylate, [0060]
1,1-dimethylpropyl-.alpha.-phenylacrylate(t-pentylatropate), [0061]
1,1-dimethylethyl-.alpha.-methylacrylate, (t-butylmethylacrylate),
and [0062] 1,1-dimethylpropyl-.alpha.-methylacrylate
(t-pentylmethacrylate).
[0063] The most preferred alkyl ester is t-butylmethacrylate which
is commercially available in high purity from Mitsubishi-Rayon,
Japan. Another source of high purity monomer can be obtained from
BASF. Mixture of the alkyl esters of above and other esters, which
do not thermally convert to anhydride groups, preferably
isobutylmethylacrylate (3-methylpropyl-.alpha.-methylacrylate), can
be used if M blocks having both ester and anhydride functional
groups are desired. Alternatively, the anhydride reaction
temperature and residence time can be reduced to afford a mixed
block of unreacted ester and six-membered anhydride.
[0064] The processes for producing the polymers of Formula I-XV
are, at least in part, rather particular because of the tendency of
the ester groups to undergo side reactions with polymer lithium
species. In the process of producing a more conventional polymer,
e.g., a block polymer of styrene and 1,3-butadiene, a variety of
process schemes are available. Such procedures include the
production by anionic polymerization of a living polymer of either
type of monomer before crossing over to the polymerization of the
other type of monomer. It is also conventional to produce such
block polymers by sequential polymerization or by the use of
coupling agents to obtain branched or radial polymers. In the
production of the polymers of the invention, the aliphatic and
aromatic portions are produced by sequential polymerization and the
ester block is then produced as a final polymerization step prior
to termination or any addition of coupling agents.
[0065] In each procedure to form a polymer of Formulas I-XV the
monomers are anionically polymerized in the presence of a metal
alkyl initiator, preferably an alkali metal alkyl. The use of such
initiators in anionic polymerizations is well known and
conventional. A particularly preferred initiator is
sec-butyllithium.
[0066] The polymerization of the alkenyl aromatic compounds takes
place in a non-polar hydrocarbon solvent such as cyclohexane or in
mixed polar/non-polar solvents, e.g., mixtures of cyclohexane and
an ether such as tetrahydrofuran or diethyl ether. Suitable
reaction temperatures are from about 20.degree. C. to about
80.degree. C. and the reaction pressure is sufficient to maintain
the mixture in the liquid phase. The resulting product includes a
living poly(alkenyl aromatic compound) block having a terminal
organometallic site which is used for further polymerization.
[0067] The polymerization of the conjugated alkadiene takes place
in a solvent selected to control the mode of polymerization. When
the reaction solvent is non-polar, the desired degree of 1,4
polymerization takes place whereas the presence of polar material
in a mixed solvent results in an increased proportion of 1,2
polymerization. Polymers resulting from about 6% to about 95% of
1,2 polymerization are of particular interest. In the case of 1,4
polymerization, the presence of ethylenic unsaturation in the
polymeric chain results in cis and trans configurations.
Polymerization to give a cis configuration is predominant.
[0068] Polymerization of the esters takes place in the mixed
solvent containing the polymerized conjugated alkadiene at a
temperature from about -80.degree. C. to about 100.degree. C.,
preferably from about 10.degree. C. to about 50.degree. C.
[0069] Subsequent to production of the acrylic block or segment,
the polymerization is terminated by either reaction with a protic
material, typically an alkanol such as methanol or ethanol or with
a coupling agent. A variety of coupling agents are known in the art
and can be used in preparing the coupled block copolymers of the
present invention. These include, for example, dihaloalkanes,
silicon halides, siloxanes, multifunctional epoxides, silica
compounds, esters of monohydric alcohols with carboxylic acids,
(e.g. methylbenzoate and dimethyl adipate) and epoxidized oils.
Star-shaped polymers are prepared with polyalkenyl coupling agents
as disclosed in, for example, U.S. Pat. Nos. 3,985,830; 4,391,949;
and 4,444,953; as well as Canadian Patent No. 716,645, each
incorporated herein by reference. Suitable polyalkenyl coupling
agents include divinylbenzene, and preferably m-divinylbenzene.
Preferred are tetra-alkoxysilanes such as tetra-methoxysilane
(TMOS) and tetra-ethoxysilane (TEOS), tri-alkoxysilanes such as
methyltrimethoxysilane (MTMS), aliphatic diesters such as dimethyl
adipate and diethyl adipate, and diglycidyl aromatic epoxy
compounds such as diglycidyl ethers deriving from the reaction of
bis-phenol A and epichlorohydrin. Coupling with a polymerizable
monomer such as divinylbenzene does not terminate the
polymerization reaction. Termination to remove the lithium is
preferred after coupling with divinylbenzene although additional
arms can be grown from the lithium sites before termination if
desired. The polymers are then recovered by well known procedures
such as precipitation or solvent removal.
[0070] The polymers produced by the above procedures will undergo
some coupling through an ester group on an adjacent living molecule
prior to termination unless the living polymer chains are first
end-capped with a unit of 1,1-diphenylethylene or
.alpha.-methylstyrene. Ester coupling occurs in about 10-50% of the
polymer by weight if left unchecked. Such coupling is often
acceptable, particularly when the desired polymer structure
requires coupling after polymerization of the esters.
[0071] The production of the polymers of Formula IV and X is
somewhat different procedurally, although the process technology is
broadly old. In this modification, conjugated alkadiene is
polymerized in the presence of a difunctional initiator, e.g.,
1,3-bis(1-lithio-1,3-dimethylpentyl)benzene, to produce a living
polyalkadiene species with two reactive organometallic sites. This
polymer species is then reacted with the remaining monomers to
produce the indicated structures.
[0072] The production of the polymers of Formula VI, XII, and XIII
and XV is also different procedurally, although the process
technology again is broadly old. In this modification, a
multifunctional initiator identified as core Z is first produced by
anionically polymerizing small molecules of living polystyrene or a
living conjugated alkadiene and coupling the small molecules with
divinylbenzene to provide numerous organometallic sites for further
polymerization.
[0073] Each B segment or block has a molecular weight from 2,000 to
500,000 prior to any coupling, preferably from 2,000 to 200,000.
Each A block has a molecular weight from 500 to 30,000 prior to any
coupling, preferably from 1,000 to 20,000. Each non-coupled M
segment or block has a molecular weight from 200 to 100,000,
preferably from 200 to 30,000, prior to conversion to an
anhydride.
[0074] In a further modification of the base polymers of Formula
II-XIII used in the invention, the base polymers are selectively
hydrogenated to reduce the extent of unsaturation in the aliphatic
portion of the polymer without substantially reducing the aromatic
carbon-carbon unsaturation of any aromatic portion of the block
copolymer. However, in some cases hydrogenation of the aromatic
ring is desired. Thus, a less selective catalyst will work.
[0075] A number of catalysts, particularly transition metal
catalysts, are capable of selectively hydrogenating the aliphatic
unsaturation of a copolymer of an alkenyl aromatic compound and a
conjugated alkadiene, but the presence of the M segment or block
can make the selective hydrogenation more difficult. To selectively
hydrogenate the aliphatic unsaturation it is preferred to employ a
"homogeneous" catalyst formed from a soluble nickel or cobalt
compound and a trialkylaluminum. Nickel naphthenate or nickel
octoate is a preferred nickel salt. Although this catalyst system
is one of the catalysts conventionally employed for selective
hydrogenation absent alkyl methacrylate blocks, other
"conventional" catalysts are not suitable for selective
hydrogenation of the conjugated alkadienes in the ester containing
polymers.
[0076] In the selective hydrogenation process, the base polymer is
reacted in situ, or if isolated is dissolved in a suitable solvent
such as cyclohexane or a cyclohexane-ether mixture and the
resulting solution is contacted with hydrogen gas in the presence
of the homogeneous nickel or cobalt catalyst. Hydrogenation takes
place at temperatures from about 25.degree. C. to about 150.degree.
C. and hydrogen pressures from about 15 psig to about 1000 psig.
Hydrogenation is considered to be complete when at least about 90%,
preferably at least 98%, of the carbon-carbon unsaturation of the
aliphatic portion of the base polymer has been saturated, as can be
determined by nuclear magnetic resonance spectroscopy. Under the
conditions of the selective hydrogenation no more than about 5% and
preferably even fewer of the units of the A and A' blocks will have
undergone reaction with the hydrogen. The selectively hydrogenated
block polymer is recovered by conventional procedures such as
washing with aqueous acid to remove catalyst residues and removal
of the solvent and other volatiles by evaporation or
distillation.
[0077] The anhydride groups in the polymers of the invention are
produced by heating the base polymers to a temperature in excess of
180.degree. C., preferably 220.degree. C. to 260.degree. C. Heating
is preferably conducted in an extruder having a devolatilization
section to remove the volatile by-products formed by combination of
two adjacent ester groups to make one anhydride group.
[0078] The polymers preferably have the following number average
molecular weights after conversion to anhydride as measured by gel
permeation chromatography:
TABLE-US-00001 Preferred Range Most Preferred Formula Min. MW.sub.n
Max. MW.sub.n Min. MW.sub.n Max. MW.sub.n I 1,000 500,000 1,000
100,000 II 1,000 1,000,000 1,000 500,000 III 1,000 2,000,000 1,000
500,000 IV 1,000 2,000,000 1,000 500,000 V 1,000 2,000,000 1,000
1,000,000 VI 1,000 2,000,000 1,000 500,000 VII 1,000 2,000,000
20,000 1,000,000 VIII 1,000 2,000,000 20,000 2,000,000 IX 1,000
2,000,000 35,000 2,000,000 X 1,000 2,000,000 1,000 650,000 XI 1,000
2,000,000 1,000 1,000,000 XII 1,000 2,000,000 1,000 1,000,000 XIII
1,000 2,000,000 1,000 1,000,000 XIV 1,000 2,000,000 1,000 200,000
XV 1,000 2,000,000 1,000 1,000,000
[0079] Both absolute and number average molecular weights are
determined by conventional GPC as described in the examples
below.
[0080] While the hybrid polymers containing predominately anhydride
groups may be used, it is likely that some of the anhydride groups
will be converted to acid groups by contact with water. In many
cases this is a desired aspect, for example in an emulsion the
anhydride groups at the surface of a polymer or formulation
particle is in contact with water and will form the acid, or an
acid salt if a base such as sodium hydroxide is added to the water.
Since the hybrid polymer in the acid or acid salt form is active as
a surfactant, it will help to stabilize the emulsion and give
stability at lower levels of low molecular weight surfactant. In
any case the range of content of the M block may vary, as shown
below. The sum of the ester, anhydride and acid forms will equal
100 wt %:
TABLE-US-00002 Wt. % Ester Wt. % Anhydride Wt. % Acid Broad Range 0
to 50% 0 to 100% 0 to 100% Preferred Range 0 to 20% 50 to 100% 0 to
50%
[0081] Carboxy functional monomers include carboxylic acids. Such
carboxylic acids preferably contain from about 3 to about 5 carbon
atoms and include, among others, acrylic acid, methacrylic acid,
itaconic acid, and the like. Acrylic acid, methacrylic acid and
mixtures thereof are preferred. Specific examples of hydroxy
functional monomers include hydroxyethyl acrylate, hydroxypropyl
acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate.
Specific examples of glycidyl functional monomers include glycidyl
methacrylate and glycidyl acrylate. Specific examples of acrylamide
functional monomers include N-alkyl (meth)acrylamides such as
t-octyl acrylamide, cyanoethylacrylates, and diacetoneacrylamide,
Other functional monomers include amine functional monomers, epoxy
functional monomers, isocyanate functional monomers and mixtures
thereof Examples of functional resins include phenolic resins,
amino resins, polyurethanes and epoxy resins. Specific examples of
metal derivatives include but are not limited to calcium oxide,
magnesium oxide, zinc oxide, calcium stearate, zinc stearate, zinc
acetate and the like. The metal derivative must be capable of
forming ionic bonds with the anhydride or acid groups on the base
polymer or with the acid or phenolic groups on the resin.
[0082] The functional monomer is added to the block copolymer in
amounts ranging from about one functional monomer per base polymer
molecule to about one functional monomer per starting anhydride and
acid group on the base polymer. Reaction conditions vary from room
temperature to 350.degree. C., preferably from room temperature to
260.degree. C. Reaction conditions depend on the specific
functional monomer. For example, monomers which contain hydroxyl
groups can react with the base polymer at room temperature, but
this reaction is slow so that it is advantageous to carry it out at
higher temperatures, but not at temperatures which will cause the
base polymer to degrade. Optionally, a catalyst can be used to aid
this reaction.
[0083] The characterization of the resulting polymer will depend on
the specific functional monomer, reactive resin, or metal
derivative reacted with the base polymer. In general, methods such
as IR and NMR combined with various separation methods can be used
to show that a chemical reaction has taken place between anhydride
and acid groups on the base polymer and reactive monomers, resins
and metal derivatives. GPC can be used for characterization if
there is a large molecular weight change as a result of reaction,
In the case of reaction giving a cured system, the resulting
polymer or formulation can be characterized in terms of insolubles
(gel level) or by mechanical and rheological properties.
Contact Adhesives
[0084] The term "contact adhesive" means an adhesive composition
which, in use, is applied to the surfaces to be adhered and is
allowed to dry, preferably to a substantially tack-free or
touch-dry state, before the surfaces are brought together to effect
a bond. According to the present invention, a method of adhering
two surfaces together comprises applying a one-part contact
adhesive composition as defined herein to the surfaces to be
adhered, and bringing the surfaces into contact with each other
after at least some of the organic liquid has evaporated.
[0085] Preferably the adhesive of this invention is non-fluid or
gel-like in a state of rest at ambient temperatures. However, owing
to its thixotropic nature it becomes fluid when agitated, for
example by stirring or vibrating.
[0086] The organic liquid may be any of those which dissolve and/or
disperse the hybrid block copolymer. Often the hybrid block
copolymer may be partly dissolved and partly dispersed by the
organic liquid. Solvents include inexpensive aliphatic hydrocarbons
such as hexane or heptane or their isomers, aromatic hydrocarbon
solvents such as toluene and xylene, and oxygenated solvents
including ketones like acetone and methyl ethyl ketone, alcohols
such as isopropyl alcohol, and esters such as ethyl acetate and
tert butyl acetate. The choice of solvent affects several
properties of the adhesive including the rate of strength
development, open time, cost, viscosity, and sprayability. Solvent
blends are often used to control properties of the adhesive.
[0087] Other ingredients may be included in the composition to
confer or modify a property. Examples of additional ingredients are
fillers, pigments, reinforcing polymeric materials such as
chlorinated natural rubber, resins of hydrocarbyl-phenols,
hydrocarbyl-phenol resin-modifying agents, magnesium oxide, resins
of amino compounds with aldehydes, polystyrene block compatible
resins and conjugated diene block compatible resins. The
polystyrene block compatible resin may be selected from the group
consisting of coumarone-indene resin, polyindene resin, poly(methyl
indene) resin, polystyrene resin, vinyltoluene-alphamethylstyrene
resin, alphamethylstyrene resin and polyphenylene ether, in
particular poly(2,6-dimethyl-1,4-phenylene ether). Such resins are
e.g. sold under the trademarks "HERCURES", "ENDEX", "KRISTALEX",
"NEVCHEM" and "PICCOTEX". Resins compatible with the hydrogenated
(conjugated diene) block may be selected from the group consisting
of compatible C.sub.5 hydrocarbon resins, hydrogenated C.sub.5
hydrocarbon resins, styrenated C.sub.5 resins, C.sub.5/C.sub.9
resins, styrenated terpene resins, fully hydrogenated or partially
hydrogenated C.sub.9 hydrocarbon resins, rosins esters, rosin
derivatives and mixtures thereof. These resins are e.g. sold under
the trademarks "REGALITE", "REGALREZ",
"ESCOREZ","OPPERA","WINGTACK" and "ARKON".
[0088] If an improvement in cohesive strength, adhesion, and upper
service temperature (resistance to flow under load above room
temperature) is desired, especially when the surfaces to be adhered
are non-porous, it is often preferred to include in the composition
a polar resin such as a hydrocarbyl-phenol and formaldehyde resin
or a resin which is a product of amino compounds and aldehydes.
Examples of hydrocarbyl-phenols are octyl, amyl and tertiary-butyl
phenols and para-cresols. Examples of amino compounds are urea and
melamine. An example of an aldehyde is formaldehyde. When a
heat-reactive hydrocarbyl-phenol resin is employed it is preferred
to employ a modifying agent such as magnesium oxide. The amount of
magnesium oxide employed may be, for example, up to 20 parts by
weight, and preferably in the range of from 1 to 10 parts by
weight, per 100 parts by weight of hybrid block copolymer in the
composition. The weight ratio of magnesium oxide: resin may
suitably be in the range 1:100 to 50:100 and is preferably in the
range 5:100 to 40:100, especially in the range 5:100 to 25:100. A
large improvement in cohesive strength is obtained when either the
base block copolymer and/or the resin can react with itself or each
other. The hybrid block copolymer can be pre-reacted with the resin
prior to application of the adhesive to improve compatibility and
storage stability of the solvent based composition. Reaction means
chemical bonds are formed. Chemical bonds include but are not
limited to covalent bonds, ionic bonds and hydrogen bonds. For
example, a contact adhesive is prepared comprising an amino resin
and the base polymer containing anhydride groups so that amide or
imide covalent bonds are formed between the resin and polymer. For
example, a contact adhesive is prepared comprising a metal
derivative such as a metal oxide or a metal salt of an acid, the
base polymer containing acid and or anhydride groups, and a resin
with acid or phenolic groups. Examples of metal derivatives include
but are not limited to calcium oxide, magnesium oxide, zinc oxide,
calcium stearate, zinc stearate, zinc acetate, lithium methoxide,
sodium methoxide, and the like. The metal derivative must be
capable of forming ionic bonds with the anhydride or acid groups on
the base polymer or with the acid or phenolic groups on the resin.
The metal derivatives include but are not limited to compounds
containing positive valent ions of Groups IA, IB, HA, IIB, IIIA,
IIIB and VIII of the Periodic Table of Elements. These metal ions
can be complexed or uncomplexed, and can be used alone or in any
mixtures thereof. Suitable monovalent metal ions are Na+, K+, Li+
among others. Suitable divalent metal ions are Mg++, Ca++, Zn++
among others. Suitable trivalent metal irons are Al+++, Sc+++ among
others. Preferable compounds are hydroxides, oxides, alcoholates,
carboxylates, formates, acetates, methoxides, ethoxides, nitrates,
carbonates, and bicarbonates of the above referenced metal ions.
See generally U.S. Pat. No. 5,516,831, col. 6, lines 8-22 for a
more complete listing of metal ions, which disclosure is herein
incorporated by reference.
[0089] The contact adhesive composition may have a total solids
content of from 10 to 70% by weight, preferably from 15 to 55% by
weight and more preferably from 20 to 50% by weight (note block
copolymers will have lower viscosity than chloroprene so can be
used at higher solids).
Solvent Based Adhesives, Sealants and Coatings
[0090] In one aspect of the present invention we have discovered a
novel adhesive composition comprising 100 parts by weight of at
least one hybrid block copolymer, 25 to 300 parts by weight of at
least one tackifying resin, 0 to 200 parts by weight of an extender
oil and a solvent or solvent mixture.
[0091] One of the components used in the adhesives and sealants of
the present invention is a tackifying resin. Tackifying resins
include both polystyrene block compatible resins and mid block
compatible resins. The polystyrene block compatible resin may be
selected from the group consisting of coumarone-indene resin,
polyindene resin, poly(methyl indene) resin, polystyrene resin,
vinyltoluene-alphamethylstyrene resin, alphamethylstyrene resin and
polyphenylene ether, in particular poly(2,6-dimethyl-1,4-phenylene
ether). Such resins are e.g. sold under the trademarks "HERCURES",
"ENDEX", "KRISTALEX", "NEVCHEM" and "PICCOTEX". Resins compatible
with the hydrogenated (mid) block may be selected from the group
consisting of compatible C.sub.5 hydrocarbon resins, hydrogenated
C.sub.5 hydrocarbon resins, styrenated C.sub.5 resins,
C.sub.5/C.sub.9 resins, styrenated terpene resins, fully
hydrogenated or partially hydrogenated C.sub.9 hydrocarbon resins,
rosins esters, rosin derivatives and mixtures thereof. These resins
are e.g. sold under the trademarks "REGALITE", "REGALREZ",
"ESCOREZ", "WINGTACK" and "ARKON".
[0092] Another one of the components used in the adhesives and
sealants of the present invention is a polymer extending oil or
plasticizer. Especially preferred are the types of oils that are
compatible with the elastomeric segment of the block copolymer.
While oils of higher aromatics content are satisfactory, those
petroleum-based white oils having low volatility and less than 50%
aromatic content are preferred. Such oils include both paraffinic
and naphthenic oils. The oils should additionally have low
volatility, preferable having an initial boiling point above about
500.degree. F.
[0093] Examples of alternative plasticizers which may be used in
the present invention are oligomers of randomly or sequentially
polymerized styrene and conjugated diene, oligomers of conjugated
diene, such as butadiene or isoprene, liquid polybutene-1, and
ethylene-propylene-diene rubber, all having a weight average
molecular weight in the range from 300 to 35,000, preferable less
than about 25,000 mol weight. The amount of oil or plasticizer
employed varies from about 0 to about 300 parts by weight per
hundred parts by weight rubber, or block copolymer, preferably
about 20 to about 150 parts by weight.
[0094] Adhesives are formulated to give a satisfactory balance of
tack, peel, shear and viscosity. Various types of fillers and
pigments can be included in the adhesive formulations to pigment
the adhesive and reduce cost. Suitable fillers include calcium
carbonate, clay, talc, silica, zinc oxide, titanium dioxide and the
like. The amount of filler usually is in the range of 0 to 30%
weight based on the solvent free portion of the formulation,
depending on the type of filler used and the application for which
the adhesive is intended. An especially preferred filler is
titanium dioxide.
[0095] If the adhesive is to be applied from solvent solution, the
organic portion of the formulation will be dissolved in a solvent
or blend of solvents. Aromatic hydrocarbon solvents such as
toluene, xylene or Shell Cyclo Sol 53 are suitable. Aliphatic
hydrocarbon solvents such as hexane, naphtha or mineral spirits may
also be used. If desired, a solvent blend consisting of a
hydrocarbon solvent with a polar solvent can be used. Suitable
polar solvents include esters such as isopropyl acetate, ketones
such as methyl isobutyl ketone, and alcohols such as isopropyl
alcohol. The amount of polar solvent used depends on the particular
polar solvent chosen and on the structure of the particular polymer
used in the formulation. Usually, the amount of polar solvent used
is between 0 and 50% wt in the solvent blend.
[0096] The compositions of the present invention may be modified
further with the addition of other polymers, oils, fillers,
reinforcements, antioxidants, stabilizers, fire retardants, anti
blocking agents, lubricants and other rubber and plastic
compounding ingredients without departing from the scope of this
invention. Such components are disclosed in various patents
including U.S. Pat. No. 3,239,478; and U.S. Pat. No. 5,777,043, the
disclosures of which are incorporated by reference.
[0097] The compositions of the present invention may be designed
for a wide variety of uses and applications. They may be applied to
paper, paper boards, wood, metal foils, polyolefin films, polyvinyl
chloride films, cellophane, felts, woven fabrics, non-woven
fabrics, glass, etc., and for bonding two or more of such materials
together. The adhesives are useful in pressure sensitive tapes,
such as masking tapes, adhesive sheets, primers for other
adhesives, adhesive tapes, mending tapes, electrical insulation
tape, laminates, hot-melt adhesives, mastics, cements, caulking
compounds, binders, sealants, delayed tack adhesives, adhesive
lattices, carpet backing, cements, etc.
[0098] Regarding the relative amounts of the various ingredients,
this will depend in part upon the particular end use and on the
particular block copolymer that is selected for the particular end
use. Table A below shows some notional compositions that are
included in the present invention.
TABLE-US-00003 TABLE A Applications, Compositions and Ranges
Composition, Application Ingredients Parts by weight Adhesive
Hybrid Polymer 100 Tackifying Resin 25 to 300 Extending Oil 0 to
200 Solvent based adhesive Hybrid Polymer 100 (not including
solvent) Tackifying Resin 25 to 300 Oil 0 to 100 Construction
adhesive or Hybrid Polymer 100 sealant Tackifying Resin 0 to 200
Endblock Resin 0 to 200 Calcium Carbonate 0 to 800
Epoxy, Urethane, and Melamine
[0099] The hybrid block copolymers of the present invention can be
prepared by reaction of the base polymer with monomers and resins
containing epoxy or isocyanate functional groups or amino resins
containing active methylol functional groups. For example, one can
prepare adhesive or coating compositions comprising a base block
copolymer and an epoxy resin, an isocyanate or an amino resin in
which the resin has reacted with the anhydride and/or acid groups
of the base polymer. The hybrid block copolymer of the present
invention which has been reacted with these resins is expected to
find uses on wood, concrete, metal and plastic substrates as
adhesives or as protective and decorative coatings. The relative
amounts of the various ingredients will depend on the specific use
but generally the ratio of block copolymer to resin or monomer will
vary from 1:20 to 20:1 and more preferably from 1:10 to 10:1. Also,
additional ingredients can be added the formulation including the
tackifying resins, oils, plasticizers, fillers, reinforcements,
antioxidants, stabilizers, fire retardants, anti blocking agents,
and lubricants disclosed in the section above on solvent based
adhesives.
Acrylic Pressure-sensitive Adhesives
[0100] The acrylic pressure-sensitive adhesive polymer of the
invention is a rubber-acrylic polymer comprising an acrylic polymer
backbone grafted with a particular functionalized block copolymer.
Pressure sensitive acrylic adhesives are typically made by solution
and emulsion polymerization. More specifically, acrylic polymer
backbone contemplated for use in the practice of the invention is
formed of acrylate monomers of one or more low Tg alkyl acrylates.
Low transition temperature monomers are those having a Tg of less
than about 0.degree. C. Preferred alkyl acrylates which may be used
to practice the invention have up to about 18 carbon atoms in the
alkyl group, preferably from about 4 to about 10 carbon atoms in
the alkyl group. Alkyl acrylates for use in the invention include
butyl acrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl
acrylate, isooctyl acrylate, decyl acrylate, dodecyl acrylates,
isomers thereof, and combinations thereof A preferred alkyl
acrylate for use in the practice of the invention is 2-ethyl hexyl
acrylate.
[0101] The monomer system used to make the acrylic backbone polymer
could be solely based on low Tg alkyl acrylate ester monomers, but
is preferably modified by inclusion of high Tg monomers and/or
functional comonomers, in particular carboxy-containing functional
monomers, and/or, even more preferably, hydroxy-containing
functional monomers.
[0102] High Tg monomer components which may be present, and in some
embodiments are preferably present, include methyl acrylate, ethyl
acrylate, isobutyl methacrylate, and/or vinyl acetate. The high Tg
monomers may be present in a total amount of up to about 50% by
weight, preferably from about 5 to about 50% by weight, even more
preferably from about 10 to about 40% by weight, based on total
weight of the hybrid polymer.
[0103] The acrylic backbone polymer may also comprise one or more
functional monomers. Preferred are carboxy and/or hydroxy
functional monomers. This may be added to the base polymer to make
the functionalized block copolymer, or the base polymer may be
added separately, and the functional monomers added with the
acrylic monomers.
[0104] Carboxy functional monomers will typically be present in the
hybrid polymer in an amount of up to about 7% by weight, more
typically from about 1 to about 5% by weight, based on the total
weight of the monomers. Useful carboxylic acids preferably contain
from about 3 to about 5 carbon atoms and include, among others,
acrylic acid, methacrylic acid, itaconic acid, and the like.
Acrylic acid, methacrylic acid and mixtures thereof are
preferred.
[0105] In a particularly preferred embodiment, the acrylic backbone
comprises hydroxy functional monomers such as hydroxyalkyl
(meth)acrylate esters, and acrylic polymers used to form the
backbone of the invention are preferably acrylic
ester/hydroxy(meth)alkyl ester copolymers. Specific examples of
hydroxy functional monomers include hydroxyethyl acrylate,
hydroxypropyl acrylate, hydroxyethyl methacrylate and hydroxypropyl
methacrylate. Hydroxy functional monomers are generally used in an
amount of from about 1 to about 10%, preferably from about 3 to
about 7%.
[0106] Other comonomers can be used to modify the Tg of the acrylic
polymer, to further enhance adhesion to various surfaces and/or to
further enhance high temperature shear properties. Such comonomers
include N-vinyl pyrrolidone, N-vinyl caprolactam,
N-alkyl(meth)acrylamides such as t-octyl acrylamide,
cyanoethylacrylates, diacetoneacrylamide, N-vinyl acetamide,
N-vinyl formamide, glycidyl methacrylate and allyl glycidyl ether,
methyl methacrylate, acrylonitrile, and styrene.
[0107] The monomer proportions of the acrylic polymer are adjusted
in such a way that the backbone polymer has a glass transition
temperature of less than about -10.degree. C., preferably from
about -20.degree. C. to about -60.degree. C.
[0108] The preferred pressure sensitive adhesive compositions are
preferably crosslinked using a chemical crosslinking agent. While
the use of aluminum and titanium crosslinking agents may be used to
practice the invention, it has been discovered that use of titanium
containing metal alkoxide crosslinker is necessary for high
temperature performance, and is the preferred crosslinker for
hydroxyalkyl(meth)acrylate esters. The use of a titanium
crosslinker imparts a yellowish color to the final product but, for
many applications, is of little concern. The crosslinker is
typically added in an amount of from about 0.3% to about 2% by
weight of the hybrid polymer.
[0109] The pressure sensitive adhesive compositions of this
invention are preferably tackified. The acrylic and rubber
components of the hybrid polymer are believed to form a microphase
separated structure in the solid state. Support for this comes from
the appearance of two distinct glass transition temperatures
revealed by the dynamic mechanical analysis of the adhesive
composition. Tackifying resins useful in these compositions are
compatible with the rubber macromer phase. Tackifiers compatible
with the acrylic phase can, of course, be used with any acrylic
polymer and the hybrid polymer of this invention is no exception.
However, such tackifiers are typically derived from natural rosin
and are associated with poor aging characteristics. It is an
objective of this invention to overcome these problems. Thus the
preferred tackifiers are synthetic hydrocarbon resins derived from
petroleum. Non-limiting examples of rubber phase associating resins
include aliphatic olefin derived resins such as those available
from Goodyear under the Wingtack.RTM. and the Escorez.RTM. 1300
series from Exxon. A common C5 tackifying resin in this class is a
diene-olefin copolymer of piperylene and 2-methyl-2-butene having a
softening point of about 95.degree. C. This resin is available
commercially under the tradename Wingtack 95. The resins normally
have ring and ball softening points as determined by ASTM method
E28 between about 20.degree. C. and 150.degree. C. Also useful are
C9 aromatic/aliphatic olefin-derived resins available from Exxon in
the Escorez 2000 series. Hydrogenated hydrocarbon resins are
especially useful when the long term resistance to oxidation and
ultraviolet light exposure is required. These hydrogenated resins
include such resins as the Escorez 5000 series of hydrogenated
cycloaliphatic resins from Exxon, hydrogenated C9 and/or C5 resins
such as Arkon.RTM. P series of resins by Arakawa Chemical,
hydrogenated aromatic hydrocarbon resins such as Regalrez.RTM.
1018, 1085 and the Regalite.RTM. R series of resins from Hercules
Specialty Chemicals. Other useful resins include hydrogenated
polyterpenes such as Clearon.RTM. P-105, P-115 and P-125 from the
Yasuhara Yushi Kogyo Company of Japan.
[0110] The tackifying resin will normally be present at a level of
5 to 50% by weight of the adhesive composition and preferably at a
level of about 10 to 40% by weight of the adhesive composition.
[0111] The formulated adhesive may also include excipients,
diluents, emollients, plasticizers, antioxidants, anti-irritants,
opacifiers, fillers, such as clay and silica, pigments and mixtures
thereof, preservatives, as well as other components or
additives.
[0112] The pressure sensitive adhesives of the invention may
advantageously be used in the manufacture of adhesive articles
including, but not limited to, industrial tapes and transfer films.
The adhesive articles are useful over a wide temperature range,
have improved UV resistance and adhere to a wide variety of
substrates, including low energy surfaces, such as polyolefins,
e.g., polyethylene and polypropylene, polyvinyl fluoride, ethylene
vinyl acetate, acetal, polystyrene, powder-coated paints, and the
like. Single and double face tapes, as well as supported and
unsupported free films are encompassed by the invention. Also
included, without limitation, are labels, decals, name plates,
decorative and reflective materials, reclosable fasteners, theft
prevention and anti-counterfeit devices.
[0113] In one embodiment, the adhesive article comprises an
adhesive coated on at least one major surface of a backing having a
first and second major surface. Useful backing substrates include,
but are not limited to foam, metal, fabric, and various polymer
films such as polypropylene, polyamide and polyester. The adhesive
may be present on one or both surfaces of the backing When the
adhesive is coated on both surfaces of the backing, the adhesive on
each surface can be the same or different.
Structural Acrylic Adhesives
[0114] Structural acrylic adhesives are well known for bonding a
wide variety of substrates. They are used as an alternative to
mechanical joining methods for a number of reasons including cost,
aesthetics, and noise reduction. The disclosed structural adhesive
compositions comprise at least two components. The first or monomer
component of the composition may have several sub-components
including a methacrylate ester monomer, additional monomers and at
least one elastomeric material. The monomer component may also
include, inter alia, adhesion promoters, cross-linked rubbers,
tertiary amine initiators, inhibitors, open-time promoters,
thixotropic agents, antioxidants, plasticizers, talc and cohesive
failure mode promoters. The second or catalyst component of the
composition includes a polymerization catalyst.
[0115] The methacrylate ester monomers include those where the
alcohol portion of the ester group contains one to eight carbon
atoms. Examples of such ester monomers are methyl methacrylate
(MMA), ethyl methacrylate, 2-ethyhexyl methacrylate, cyclo-10 hexyl
methacrylate, lauryl methacrylate and mixtures thereof. The
methacrylate ester monomers also include less volatile
monofunctional methacrylates such as tetrahydrofurfuryl and
hydroxyethyl esters. The preferred ester monomers are MMA,
tetrahydrofurfuryl methacrylate and lauryl methacrylate
[0116] Additional monomers which may be used in combination with
the methacrylate ester monomers are acrylate esters wherein the
alcohol portion of the ester contains one to eight carbon atoms,
examples of which are methyl acrylate, ethyl acrylate, butyl
acrylate and 2-ethyhexyl acrylate. Other useful monomers are
acrylonitrile, methacrylonitrile, styrene, vinyl toluene, and the
like.
[0117] Other additional monomers which may be used in combination
with the methacrylate ester monomers are polymerizable
ethylenically unsaturated mono or polycarboxylic acids. Acrylic
acid, methacrylic acid (MAA), isophthalic acid (EPA), crotonic
acid, maleic acid and fumaric acid are examples of such acids. The
preferred acids are MAA or IPA.
[0118] The elastomeric material used in these structural adhesive
compositions is the hybrid block copolymer of the present
invention. Preferably, the hybrid block copolymer is a reaction
product of the base block copolymer with anhydride and acid groups
with a multifunctional monomer which contains both a functional
group that reacts with the anhydride or acid group of the base
polymer and a functional group that will react with the monomer
component of the structural adhesive in a free radical process. The
latter functional group is preferably either an acrylate or
methacrylate double bond. Examples of the multifunctional monomer
include but are not limited to glycidyl acrylate, glycidyl
methacrylate, hydroxy ethyl acrylate and hydroxy ethyl
methacrylate.
[0119] The tertiary amine initiator helps accelerate the reaction
of the methacrylate ester monomers with the polymerization catalyst
and is selected from N,N-dimethylaniline, N,N-dimethyltoluidine
(DMT), N,N-diethylaniline, N,N-diethyltoluidine,
N,N-bis[dihydroxyethyl]-p-toluidine,
N,N-bis[dihydroxypropyl]-p-toluidine and the like.
[0120] While any order may be utilized for the addition of
sub-components of the monomer component, the preferred order is as
follows. To the elastomer solution(s), the cohesive failure mode
promoter solution is added, if present. Then the remaining neat
methacrylate ester monomer is added, followed by the plasticizer,
the adhesion promoter, the open time promoter, the antioxidant, the
inhibitor, the additional monomers, and the tertiary amine
initiator. All sub-components are not necessarily included in each
monomer component. The included sub-components are mixed. Next, the
talc, and the cross-linked rubber are added while slowly increasing
the mixing speed. Next, the thixotropic agent is added and mixing
is continued. The mixing machine is stopped and the mixture is
allowed to sit. To insure that the thixotropic agent is properly
activated and to insure that the cross-linked rubber is fully
swelled, the mixture may be mixed and allowed to sit repeatedly.
After it is allowed to sit, the mixture is mixed to create a
uniform consistency. Finally, the mixture is mixed under a vacuum
to remove any entrapped air. Generally, the amount of the
methacrylate ester monomer may be increased to compensate for
losses attributed to the application of the vacuum.
[0121] The catalyst component of the composition is a
polymerization catalyst. Suitable catalysts include free radical
generators which trigger the polymerization of the monomer
component. Such catalysts are peroxides, hydroperoxides, peresters,
and peracids. Examples of these catalysts are benzoyl peroxide,
cumene hydroperoxide, tertiary butyl hydroperoxide, dicumyl
peroxide, tertiary butyl peroxide acetate, tertiary butyl
perbenzoate, ditertiary butyl azodiisobutyronitrile and the like.
Radiant energy, e.g., ultraviolet light, and heat, may also be used
as a catalyst. The preferred catalyst is a paste of 18 wt %
anhydrous benzoyl peroxide.
[0122] The total elastomer content will be 5-50% to ensure
toughness and flexibility. The hybrid polymer can be combined with
other elastomers to make up the total elastomer content. Preferably
the hybrid polymer is added at 5-20% to ensure low viscosity.
Acrylic Sealants and Coatings
[0123] Acrylic sealants and coatings comprise the elastomeric block
copolymers of the present invention, an acrylic ester and a monomer
which gives flexibility. Typically hard acrylic esters like methyl
methacrylate, vinyl acetate, and methyl acrylate are used in
combination with monomers which give flexibility including butyl
acrylate and 2-ethylhexyl acrylate.
Radiation Cured Adhesives, Sealants, Coatings and Printing
Plates
[0124] The base polymers of the present invention can be converted
to radiation curable polymers simply by reaction with a monomer
which contains both a functional group that reacts with the
anhydride or acid group of the base polymer and a functional group
that is radiation curable, for example an acrylic, epoxy or thiol
moiety. Examples of such monomers include but are not limited to
glycidyl acrylate, glycidyl methacrylate, hydroxy ethyl acrylate
and hydroxy ethyl methacrylate. These reaction products are hybrid
block polymers which are radiation curable and can be used to
formulate adhesives, sealants, coatings and printing plates both
from solution, hot melt, and from water based dispersions. They can
be used as the primary ingredient in the formulation or can be used
as an additive in the formulation. The formulations are similar to
non radiation cured adhesives, sealants and coatings except that
they also contain initiators that react after irradiation, and can
also contain other monomers, oils, resins, and polymers that react
though the radiation initiated chemistry.
[0125] In UV cure, for example, a photoinitiator is included in the
formulation. It is also possible to employ electron beam curing.
Also, multifunctional monomers such as di and tri acrylates can be
added to the formulation to improve and speed the cure. For
example, the hybrid polymer with acrylic functionality can be mixed
with an acrylic monomer and initiator, processed into an adhesive,
sealant, coating or printing plate, and then cured via radiation.
The hybrid radiation curable polymer is combined with a
photoinitiator, optionally a multifunctional acrylic monomer,
optionally other radiation curable monomers and polymers such as
non-hydrogenated and selectively hydrogenated styrenic block
copolymers, optionally other radiation curable plasticizers and
resins such as liquid polybutadiene and polyisoprene oils, and
optionally other formulating ingredients such as the tackifying
resins, oils, plasticizers, fillers, reinforcements, antioxidants,
stabilizers, fire retardants, anti blocking agents, and lubricants
disclosed in the section above on solvent based adhesives.
Melt Processes and Water Based Processes
[0126] It is often desirable to carry out processes in the melt so
that costly solvent or water removal steps can be avoided. The
hybrid polymers of the present invention can be prepared in
solvent, water based emulsions and dispersions, and melt processes
by methods well known in the art. For example, an acrylic copolymer
with reactive functional groups can be mixed with the base block
copolymer with acid or anhydride groups in a batch mixer or
extruder prior to or during preparation of the adhesive, sealant or
coating. Other formulating ingredients can be present or added
during the mixing process. For example, an acrylic or epoxy monomer
or a melamine resin or a metal derivative can be reacted with the
base block copolymer with acid or anhydride groups in a batch mixer
or extruder. The reaction of the starting block copolymer with TBMA
endblocks to form the base block copolymer with acid or anhydride
groups can be done in the same melt process step in which the
reaction with reactive monomer, resin or metal derivative
occurs.
[0127] Water based processes are also of interest because of
environmental restrictions on solvent emissions and because water
based emulsions and dispersions have low viscosity. The base block
copolymer with acid or anhydride groups can be added to reactive
monomers or resins or metal derivatives, and this mixture dispersed
or emulsified in water so that the hybrid block copolymer is formed
in a water based system or after application and further treatment
of the water based product. Alternatively the hybrid block
copolymer can be prepared and then formulated and this formulation
can be dispersed or emulsified in water.
EXAMPLES
[0128] The following examples are provided to illustrate the
present invention. The examples are not intended to limit the scope
of the present invention and they should not be so interpreted.
Amounts are in weight parts or weight percentages unless otherwise
indicated.
Example 1
Preparation of Block Copolymers: Polymer #1, Polymer #2, Polymer
#3
[0129] Polymer #1 was polymerized in the solvent mixture comprising
90% cyclohexane and 10% diethyl ether. Styrene was polymerized in
the step I reactor and the living polymer was transferred to the
step II reactor for sequential polymerization of butadiene followed
by tert-butyl methacrylate ("TBMA"). The polymerization was
terminated with methanol. 1.61 kg of TBMA and 37.5 kg of total
monomer were charged for a target polymer TBMA content of 4.3% wt.
The peak molecular weights in polystyrene equivalents were
characterized by GPC with UV detector at each step: 7,054 after
styrene polymerization, 122,425 after BD polymerization, and a
mixture of 67% of a material with 127,043 molecular weight and 33%
of a species with 250,264 molecular weight after TBMA
polymerization. The reaction mixture was analyzed by NMR after TBMA
polymerization and shown to contain no unreacted monomer within
detection limits. The polymer was hydrogenated with a cobalt
catalyst, washed with dilute phosphoric acid, neutralized with
ammonia and stabilized with 0.1% Irganox 1010. The hydrogenated
polymer cement was analyzed by NMR. The hydrogenated polymer
contained 9.5% styrene, a residual unsaturation of 0.12 meq/gm, and
a 1,2 BD content of 39.6%. The S-EB-TBMA polymer was recovered by
cyclone finishing and dried in an air circulating oven.
[0130] Polymer #2 was polymerized in the solvent 90%
cyclohexane/10% diethyl ether. Styrene was polymerized in the step
I reactor and the living polymer was transferred to the step II
reactor for sequential polymerization of butadiene followed by
TBMA. The polymerization was terminated with methanol. 3.08 kg of
TBMA and 37.5 kg of total monomer were charged for a target polymer
TBMA content of 8.2% wt. The peak molecular weights in polystyrene
equivalents were characterized by GPC with UV detector at each
step: 7,117 after styrene polymerization, 127,360 after BD
polymerization, and a mixture of 66% of a material with 130,562
molecular weight and 34% of a species with 256,135 molecular weight
after TBMA polymerization. The reaction mixture was analyzed by NMR
after TBMA polymerization and shown to contain no unreacted monomer
within detection limits. The polymer was hydrogenated with a cobalt
catalyst, washed with dilute phosphoric acid, neutralized with
ammonia and stabilized with 0.1% Irganox 1010. The hydrogenated
polymer cement was analyzed by NMR. The hydrogenated polymer
contained 9.2% styrene, a residual unsaturation of 0.20 meq/gm, and
a 1,2 BD content of 39.5%. The S-EB-TBMA polymer was recovered by
cyclone finishing and dried in an air circulating oven.
[0131] Polymer #3 was prepared by sequential polymerization in 90%
cyclohexane/10% diethyl ether of 30 kg of butadiene followed by 7.5
kg of TBMA. The polymerization was terminated with methanol. The
target polymer TBMA content was 20%. The peak molecular weights in
polystyrene equivalents were characterized by GPC with refractive
index detector at each step: 113,106 after BD polymerization and a
mixture of 62% of a material with 116,479 molecular weight and 38%
of a species with 226,980 molecular weight after TBMA
polymerization. The polymer was hydrogenated with a cobalt
catalyst, washed with dilute phosphoric acid, neutralized with
ammonia and stabilized with 0.1% Irganox 1010. The EB-TBMA polymer
was recovered by hot water coagulation.
Conversion of Block Copolymers to Anhydride Form
[0132] The polymers were converted to the anhydride/acid form by
extruding with a Berstoff 25 mm twin screw co-rotating extruder.
Two examples are given below:
Extruder Conditions
TABLE-US-00004 [0133] POLYMER #1A POLYMER #1B Actual temperature
.degree. C. Zone 1 250 220 Zone 2 250 220 Zone 3 255 225 Zone 4 255
225 Zone 5 260 230 Zone 6 260 230 Zone 7 260 230 Extruder speed rpm
200 198
[0134] IR spectroscopy showed that the S-EB-MAAn polymers were
substantially converted from the TBMA ester to the TBMA anhydride
form. Polymer #1 has an IR absorption peak at about 1726 cm.sup.-1
which is characteristic of the ester group. After extrusion,
Polymer #1A and Polymer #1B have virtually no peak at 1726
cm.sup.-1 and have IR absorption peaks at about 1800 cm.sup.-1 and
1760 cm.sup.-1. These are characteristic peaks for the anhydride
group.
Example 1a
[0135] Polymer #4 is an S-EB-TBMA triblock copolymer with a
polystyrene block molecular weight of 6,695 (Molecular weight is
measured according to the method in Example 1, peak molecular
weights in polystyrene equivalents characterized by GPC). The S-EB
block molecular weight of 99,184 and the peak molecular weight of
the full molecule with the TBMA is 102,800. The TBMA content is
about 13 wt % and the polystyrene content is 9 wt %. The GPC
analysis revealed 31% of a species with 250,264 molecular weight
after TBMA polymerization.
Prophetic Example 2
Toughened Epoxy Composition
[0136] 270 grams of aromatic epoxy resin, the diglycidyl ether of
bis phenol A, having an epoxide equivalent weight of 190 (Epon 828
from Hexion) is heated to 130.degree. C. in a 400 ml beaker on a
hot plate. 30 grams of S-EB-MAAn (extruded Polymer #2) is mixed in
using a Silverson Model L2Air high shear mixer. After the polymer
is mixed in to the resin, the temperature is raised to 190.degree.
C. and mixing is continued for 30 minutes. This rubber modified
epoxy resin at room temperature is a hazy, thick liquid.
[0137] 90 grams of the rubber modified epoxy resin is mixed with 10
grams of toluene. This is mixed with 130 grams of an aliphatic
polyamine adduct having an amine equivalent weight of 200 (Curing
Agent C111 from Hexion). The composition is coated onto a steel
panel. After one week cure at room temperature, the composition is
a coating having good impact resistance.
Prophetic Example 3
Ambient Cure Urethane Compositions
[0138] 16.7 grams of S-EB-MAA (extruded Polymer #2+ atmospheric
moisture) having an acid equivalent weight of 1670 is dissolved in
150 grams of toluene (10% w solids). 4.05 grams of aromatic
polyisocyanate having an NCO equivalent weight of 405 (Mondur CB-60
from Bayer) is added, making a composition at 1/1 NCO/COOH. After
mixing 1 hour on a shaker, the composition is coated onto a steel
panel. After one week cure at room temperature, the composition is
a polyurethane coating.
[0139] 16.7 grams of S-EB-MAA (extruded Polymer #2+ atmospheric
moisture) having an acid equivalent weight of 1670 is dissolved in
150 grams of toluene (10% w solids). 3.65 grams of aliphatic
polyisocyanate having an NCO equivalent weight of 365 (Vestanat T
1890 L from Degussa) is added, making a composition at 1/1
NCO/COOH, and 0.2 grams of dibutyl tin dilaurate (DBTDL) is added.
After mixing 1 hour on a shaker, the composition is coated onto a
steel panel. After one week cure at room temperature, the
composition is a polyurethane coating.
[0140] 16.7 grams of S-EB-MAA (extruded Polymer #2+ atmospheric
moisture) having an acid equivalent weight of 1670 is dissolved in
150 grams of toluene (10% w solids). 10.95 grams of aliphatic
polyisocyanate having an NCO equivalent weight of 365 (Vestanat T
1890 L) is added, making a composition at 3/1 NCO/COOH, and 0.6
grams of dibutyl tin dilaurate (DBTDL) is added. After mixing 1
hour on a shaker, the composition is coated onto a steel panel.
After one week cure at room temperature, the composition is a
polyurethane/polyurea coating.
Prophetic Example 4
Bake Cure Compositions
[0141] 16.7 grams of S-EB-MAA (extruded Polymer #2+ atmospheric
moisture) having an acid equivalent weight of 1670 is dissolved in
150 grams of toluene (10% w solids). 9.3 grams of blocked aliphatic
polyisocyanate having an NCO equivalent weight of 930 (Desmodur
BL-1260A from Bayer) is added, making a composition at 1/1
NCO/COOH, and 0.2 grams of dibutyl tin dilaurate (DBTDL) is added.
After mixing 1 hour on a shaker, the composition is coated onto a
steel panel. The coated panel is baked 20 minutes at 160.degree. C.
to give a composition which is a polyurethane coating.
[0142] 9.0 grams of S-EB-TBMA (Polymer #2) is dissolved in 90 grams
of toluene (10% w solids). 1.0 gram of hexamethoxy melamine resin
(Cymel 303 from Cytec) and 0.02 grams of dodecyl benzene sulfonic
acid (Cycat 600 from Cytec) is added. After mixing 1 hour on a
shaker, the composition is coated onto a steel panel. The coated
panel is baked 10 minutes at 190.degree. C. to give a composition
which is a melamine cured coating.
Prophetic Example 5
Contact Adhesives
[0143] 100 grams of S-EB-MAA (extruded Polymer #1+ atmospheric
moisture) are added to the following formulations by mixing in ajar
on a lab roller mixer:
TABLE-US-00005 Component Parts by Weight #1 #2 #3 #4 #6 Extruded
9207 100 100 100 100 100 Schenectady SP-154 40 40 Magnesium Oxide
(a) 10 Aluminum acetyl acetonate (a) 10 Cymel 303 40 Cycat 600 4
Piccotac 5140 40 SA120M low mwt PPE 40 Pentalyn HE 10 10 Irg 1010
phenolic AO 2 2 2 2 2 Solvent Blend 608 584 608 608 608 (a)
Magnesium oxide and AlAcAc are added to the formulations as
masterbatchs, i.e. as 10% solids dispersions in toluene. The best
results are obtained by further homogenizing formulations which
contain an inorganic solid such as magnesium oxide and AlAcAc. This
can be accomplished with mixers such as Silverson Model L2Air high
shear mixer, mixers with vertical and horizontal blades such as
those produced by the Jiffy Mixer Co., and even simple propeller
mixers used to homogenize paints.
[0144] Here, Schenectady SP-154 is a mixed alkyl phenol heat
reactive resin with melting point of about 80.degree. C. supplied
by the SI Group, Cymel 303 is a hexamethoxymelamine resin supplied
by Cytec. Cycat 600 is dodecylbenzene sulfonic acid supplied from
Cytec. Picco 5140 is an aromatic resin with softening point
141.degree. C. supplied by Eastman. Pentalyn HE is an ester of
hydrogenated rosin supplied by Eastman. SA120M is a low molecular
weight polyphenylene ether supplied by General Electric.
[0145] These compositions are coated onto test substrates of
particle board and laminate (Formica) at a dry coat weight of about
2.5 gm/ft.sup.2. They are also coated onto canvas with two coats so
that a uniform coat is produced. The coated substrates and canvas
are allowed to dry for 24 hours before either bonding or putting a
second coat onto the canvas. After the coated substrates and canvas
are dried, they are pressed together with a Carver press at 35 psi
and 160.degree. C. to form 180.degree. peel samples (canvas to
particle board) and lap shear strength samples of particle board to
laminate. These solvent based contact adhesive formulations exhibit
low viscosity, good adhesion to a variety of substrates, and good
cohesive strength at elevated temperature.
Prophetic Example Example 6--Preparation of Macromonomer
[0146] The reaction was carried out in a 3-neck, 1 liter glass
round bottom flask equipped with a motorized stirrer, water
condenser and nitrogen inlet/outlet and addition funnel. An amount
of S-EB-TBMA that was previously converted quantitatively to the
anhydride/acid form (see Example 1) was dissolved in toluene to
give a 10 wt % solution. To this polymer solution was added
glycidyl methacrylate ("GMA") and tri-isobutyl amine as catalyst.
An initial sample was removed for NMR analysis.
[0147] The reaction mixture was then heated to reflux
(approximately 100.degree. C.) and stirred under a nitrogen flow
for one hour. After cooling to ambient temperature, a second sample
was removed for NMR analysis. The ratio of unreacted epoxy to
opened epoxy was used as a measure of reaction yield. The yield was
determined using proton NMR. The macromonomer could be isolated and
purified from any unreacted GMA. However, the unpurified
macromonomer can be used directly for a copolymerization with other
acrylic monomers to form the hybrid adhesive. Any unreacted GMA
will copolymerize as outlined in the next step of Example 7.
Prophetic Example 7--Preparation of the Hybrid Acrylic
Pressure-Sensitive Adhesive via Copolymerization of Macromonomer
with Acrylic Monomer
[0148] The reaction was carried out in the same 3-neck, 1 liter
glass round bottom flask that contained the macromonomer as
described in Example 6 above. 2-ethylhexyl acrylate, ethylacetate
and hexane were added to the preexisting macromonomer/toluene
solution. 2,2'-azobisisobutyronitrile (AIBN) dissolved in hexane
was then added. The reaction mixture was slowly heated to reflux
and stirred for two hours. After cooling, the reaction mixture was
precipitated in methanol to aid in the removal of any unreacted
monomers. The resultant solid copolymer was a tacky white
solid.
Working Example 6a--Preparation of Macromonomer
[0149] The reaction was carried out in a 3-neck, 1 liter glass
round bottom flask equipped with a motorized stirrer, water
condenser, nitrogen inlet/outlet and addition funnel. 1.0 gram of
block copolymer Polymer #4 (anhydride form, converted in an
extruder), 3.0 grams 2-hydroxy ethylacrylate, 11.0 g cyclohexane
and 3.0 g ethyl acetate were combined and stirred at room
temperature to dissolve the block copolymer. The temperature was
raised to about 80.degree. C. (reflux point) and the reaction
mixture was stirred for 4 hours. FT-IR confirmed the addition of
some of the 2HEA monomer as evident by the growth of the carboxylic
acid band at 1705 cm.sup.-1.
Working Example 7a--Preparation of the Hybrid Acrylic
Pressure-Sensitive Adhesive via Copolymerization of Macromonomer
with Acrylic Monomer
[0150] To the cooled reaction mixture of example 6 was added 17
grams of n-butyl acrylate and 0.05 gram AIBN initiator. The mixture
was again brought to reflux for 2 hours for the free radical
copolymerization. The bulk macromonomer solution was cooled back to
room temperature and 1 gram of Regalrez 1018, 2 grams of Regalrez
1085, 0.5 grams Drakeol 34 and 54 grams of toluene was added and
stirred to make a homogeneous solution. This mixture was used
directly for the 180 degree peel tests.
Adhesion Data
[0151] The formulated macromonomer-based adhesive of example 7 gave
an improved peel value of 1.1 pli to the polyethylene panel;
[0152] Those skilled in the art would know that many variations of
this macromonomer approach could be envisioned. For example, the
functional acrylic monomer could contain a number of other reactive
moieties capable of reacting with the glutaric anhydride such as
epoxies (glycidyl acrylates), isocyanates and/or carboxylic acids
(acrylic or methacrylic acid that form hydrogen bonds with the
anhydride).
Prophetic Example 8--Preparation of Comparative Control
[0153] In this example, a homopolymer of 2-ethylhexyl acrylate was
prepared without the macromonomer. The reaction was carried out in
a 3-neck, 1 liter glass round bottom flask equipped with a
motorized stirrer, water condenser and nitrogen inlet/outlet and
addition funnel. N-hexyl acrylate, ethylacetate and hexane were
added to the flask. AIBN dissolved in hexane was then added. The
reaction mixture was slowly heated to reflux and stirred for two
hours. The viscosity of the reaction mixture has clearly increased.
After cooling, the reaction mixture was precipitated in methanol to
aid in the removal of any unreacted monomers.
Working Example 8a--Preparation of Comparative Control
[0154] In this example, a homopolymer of n-butyl acrylate was
prepared without the macromonomer and used as the control for 180
degree peel measurement shown in Example 7. The reaction was
carried out in a 3-neck, 1 liter glass round bottom flask equipped
with a motorized stirrer, water condenser and nitrogen inlet/outlet
and addition funnel. 30 grams N-butyl acrylate, ethylacetate and
hexane were added to the flask. 25 mg of AIBN dissolved in hexane
was then added. The reaction mixture was slowly heated to reflux
and stirred for 5 hours. The viscosity of the reaction mixture had
clearly increased. After cooling, the reaction mixture was
precipitated in methanol to aid in the removal of any unreacted
monomers. The isolated polymer was a sticky white solid.
Adhesion Data
[0155] Control Peel value for unmodified poly(nbutyl acrylate) to
polyethylene was measured to be 0.46 pli.
Prophetic Example 9--Preparation of Comparative Control
[0156] In this example the homopolymer of ethylhexyl acrylate was
physically mixed with the polymer Polymer #1 using toluene as
solvent. This physical blend was used to demonstrate the difference
between blend and the case where the macromonomer is copolymerized
with acrylic monomer to form the hybrid adhesive.
Prophetic Example 10--Preparation of Functional Acrylic Copolymer
Containing Reactive Comonomer
[0157] The reaction was carried out in a 3-neck, 1 liter glass
round bottom flask equipped with a motorized stirrer, water
condenser and nitrogen inlet/outlet and addition funnel.
2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, ethylacetate and
hexane were added to the flask. AIBN dissolved in hexane was then
added. The reaction mixture was slowly heated to reflux and stirred
for two hours. The viscosity of the reaction mixture was expected
to increase. After cooling, the reaction mixture was precipitated
in methanol to aid in the removal of any unreacted monomers. Proton
NMR is expected to reveal a copolymer that contained 2-hydroxyethyl
acrylate into the copolymer.
Working Example 10a--Preparation of Functional Acrylic Copolymer
Containing Reactive Comonomer
[0158] A copolymer of n-butyl acrylate (NBA) and 2-hydroxyl ethyl
acrylate (2HEA) was prepared by free radical polymerization of 20
grams of n-butyl acrylate and 5 grams of 2-hydroxyl ethyl acrylate
in ethylacetate solvent. AIBN (25mg) was added to the reactor and
the temperature was raised until the solvent was refluxing at about
66.degree. C. The reaction was allowed to stir at reflux for 4
hours. The acrylic copolymer was isolated by precipitation in
methanol/water (90/10 v/v). The precipitation solvents contained
0.1 wt % Irganox 1010 stabilizer. The copolymer was dried in a
vacuum oven for 24 hours at 50.degree. C.
[0159] Proton NMR confirmed that the copolymer contained 21.6 wt %
2HEA repeat units. GPC showed a very broad molecular weight
distribution with a peak molecular weight (relative to polystyrene
standard) of 50,300 g/mol. The acrylic copolymer was a sticky white
solid.
Prophetic Example 11--Preparation of Hybrid Acrylic
Pressure-Sensitive Adhesive by Reaction of the Anhydride-Functional
Block Copolymer and the Hydroxyl-Functional Acrylic Copolymer
[0160] This example shows an alternative synthetic method to
prepare a hybrid PSA by taking the hydroxyl functional acrylic
copolymer of Example 10 and allowing these hydroxyl groups to react
with the anhydride rings of the functional block copolymer via an
alcoholysis reaction.
[0161] The hydroxyl-functional acrylic copolymer of Example 10 was
dissolved in toluene. A separate solution of toluene and an
anhydride/acid functionalized block copolymer (S-EB-MAA) was shaken
until fully dissolved. The two polymer solutions were mixed
together and heated to reflux for 4 hours in the reaction apparatus
already described. NMR will be used to measure the disappearance of
the hydroxyl group (2HEA unit) as a way to monitor the extent of
reaction.
Working Example 11--Preparation of Hybrid Acrylic
Pressure-Sensitive Adhesive by Reaction of the Anhydride-Functional
Block Copolymer and the Hydroxyl-Functional Acrylic Copolymer
[0162] This example shows an alternative synthetic method to
prepare a hybrid PSA by taking the hydroxyl functional acrylic
copolymer of Example 10 and allowing these hydroxyl groups to react
with the anhydride rings of the functional block copolymer via an
alcoholysis reaction.
Formulation A
[0163] 100 phr Polymer #1 (glutaric anhydride form) [0164] 200 phr
Regalrez 1085 resin (Eastman Chemical Co.) [0165] 100 phr Regalrez
1018 liquid resin (Eastman Chemical Co.) [0166] 50 phr Drakeol 34
mineral oil (Penreco) [0167] 3 phr Irganox 1010 antioxidant (Ciba
Chemical Co.)
[0168] This formulation was dissolved in an 80/20 mixture of
toluene/ethylacetate to afford a 20 wt % solution
[0169] In a separate reactor, the following mixture of the acrylic
copolymer was prepared:
Acrylic Copolymer Solution B
[0170] 20 grams n-butyl acrylate-co-2-hydroxethyl acrylate
copolymer (from Example #10) [0171] 80 grams toluene [0172] 20
grams ethyl acetate [0173] 0.2 grams Irganox 1010
[0174] The two formulations were mixed together in a 3-neck, 1
liter glass round bottom flask equipped with a motorized stirrer,
water condenser, nitrogen inlet/outlet and addition funnel. The
mixtures were combined such that 1 gram of formulation A was
combined with 20 grams of acrylic copolymer solution B. The mixture
was heated to reflux (about 85.degree. C.) for one hour. This
reaction mixture was used directly for the 180.degree. Peel
measurement against a polyethylene panel.
Adhesion results: [0175] 180.degree. Peel (pli) Stainless steel:
1.93 pli [0176] 180.degree. Peel (pli) Polyethylene: 1.43 p1i
[0177] Improved adhesion was observed versus the control from
working Example 10a (acrylic copolymer alone) that had an average
180.degree. Peel to polyethylene of 0.70 pli .
Prophetic Example 12--Hot Melt Preparation to Produce a Hybrid
PSA
[0178] The process to produce novel hybrid acrylic
pressure-sensitive adhesives with the block copolymers of this
invention is not limited to solvent-based chemistries. Both the
functional acrylic copolymer and the anhydride-containing block
copolymers can be mixed and reacted in the solid state to form
useful compositions basically equivalent to the solvent-based
examples. The mixing can be accomplished in extruders, open mixers
or high shear mixers.
[0179] In this example, a copolymer of n-butyl acrylate (NBA) and
2-hydroxyl ethyl acrylate (2HEA) was prepared by free radically
polymerizing 20 grams of n-butyl acrylate and 5 grams of 2-hydroxyl
ethyl acrylate in ethylacetate solvent. AIBN (25 mg) was added to
the reactor and the temperature was raised until the solvent was
refluxing at about 66.degree. C. The reaction was allowed to stir
at reflux for 4 hours. The acrylic copolymer was isolated by
precipitation in methanol/water (90/10 v/v). The precipitation
solvents contained 0.1 wt % Irganox 1010 stabilizer. The copolymer
was dried in a vacuum oven at about 50.degree. C.
[0180] Proton NMR confirmed that the copolymer contained about 21.6
wt % 2HEA repeat units. GPC showed a very broad molecular weight
distribution with a peak molecular weight (relative to polystyrene
standard) of 50,300 g/mol. The acrylic copolymer was a sticky white
solid.
[0181] The anhydride form of the hybrid block copolymer Polymer #1
(1 gram) and NBA-HEA acrylic copolymer (1 gram) was dissolved in
toluene/ethylacetate (90/10 v/v). A film was cast on an aluminum
sheet with a release coating. The dried film of this polymeric
blend was slightly opaque suggesting the two polymeric components
where phase separated. This film was then compressed and heated in
a Carver Press device with a temperature of 150.degree. C. for 10
minutes to induce an alcoholysis reaction between the hydroxyl
groups of the acrylic copolymer (the 2HEA units) and the glutaric
anhydride of the Polymer #1 block copolymer. The resulting
polymeric product was a tacky, rubbery solid with moderate tensile
strength. The product was soluble in THF and the cast film was
transparent suggesting the reaction had occurred to join the
acrylic copolymer to the block copolymer.
[0182] Once determining that a hybrid, or graft copolymer, could be
prepared between a functionalized acrylic copolymer and the
anhydride containing block copolymer, a larger sample was prepared
using this hot melt method. Moreover, a hydrogenated tackifying
resin was added to lower the modulus of the EB rubber phase.
[0183] The 180 degree peel was measured to a polyethylene film
which is a well known low surface energy substrate. Compared to the
unmodified acrylic copolymer, the hybrid graft polymer
(S-EB-MAA-g-NBA-2HEA) had enhanced adhesion to the LSE substrate.
This example also demonstrates that hybrid adhesives can be
prepared as solvent-based systems or as hot melt systems.
TABLE-US-00006 NBA-2HEA Hybrid copolymer Example # 180.degree.
peel--substrate (pli) to polyethylene
Working Example 12a--Preparation of Hybrid Acrylic
Pressure-Sensitive Adhesive by Reaction of the Anhydride-Functional
Block Copolymer and the Hydroxyl-Functional Acrylic Copolymer
[0184] This example differs from Example 11 in that another hybrid
block copolymer structure was used, the diblock copolymer Polymer
#3. This polymer has an EB rubber block of about 60,000 g/mol and a
TBMA polymeric block of about 15,000 g/mol. This diblock copolymer
was converted in an extruder to produce the glutaric anhydride
block. This hybrid block copolymer does not contain an additional
glassy polystyrene block. A modified acrylic adhesive was prepared
as follows:
Formulation A
[0185] 100 phr of Polymer #3 [0186] 120 phr of Regalrez 1085 resin
[0187] 5 phr Drakeol 34 [0188] 1 phr Irganox 1010
[0189] This formulation was prepared as a 20 wt % solution in 80/20
toluene/ethyl acetate
Acrylic copolymer Solution
[0190] A 20 wt % solution of the NBA-co-2HEA copolymer (Example
#10) was prepared in 10 grams of toluene and 2 grams of
ethylacetate.
Modified Acrylic Pressure Sensitive Adhesive
[0191] 3.0 grams of Formulation A was mixed with 1.degree. grams of
the acrylic copolymer solution and heated to reflux for 4 hours.
The reaction mixture was observed to increase in viscosity but did
not gel. The resulting grafted product was used directly to coat
substrates for adhesion testing.
Adhesion results: [0192] 180.degree. Peel (pli) Stainless steel:
2.5 pli [0193] 180.degree. Peel (pli) Polyethylene: 2.5 pli
[0194] Improved adhesion was observed versus the control from
working Example 10a (unmodified acrylic copolymer) that has an
average 180.degree. Peel to polyethylene of 0.70 pli
Prophetic Example 13--Low Surface Energy (LSE) Performance of the
Hybrid Pressure Sensitive Adhesives
[0195] In these examples, the 180.degree. Peel to polyethylene film
was measured using a standard ASTM test. The hybrid adhesives were
prepared by making a 10 wt % solution of the hybrid copolymer and
hydrogenated tackifying resin. The adhesive/resin solutions were
prepared coating the adhesive on to a Mylar tape. The solvent was
removed in a vacuum oven prior to testing.
Prophetic Example 14--Structural Acrylic Adhesive
[0196] The macromonomer of Example 6 was used to prepare and test
structural acrylic adhesives by the methods described in U.S. Pat.
No. 6,989,416. The catalyst component was an 18% benzoyl peroxide
paste. A ratio of 10:1 (monomer component: catalyst component) was
utilized.
[0197] To use the structural adhesive, the monomer component was
combined with the catalyst component and applied to the work pieces
which were then bonded together. The tensile strength, the
elongation and the modulus of the resultant compositions were
measured according to procedures set forth in ASTM D638-95, while
the lap shear strength was measured according to ASTM D1002-94. The
elastic recovery of a composition was calculated by creating
strength versus stress curve based on the modulus of the
composition. The linear portion of the curve corresponds to the
elastic recovery of the composition.
[0198] A 35% solution of the macromonomer from Example 6 in methyl
methacrylate was prepared and a 1% solution of naphthoquinone in
methyl methacrylate was prepared. Additionally, a 10% solution of
IGI 1977 (wax) in xylene was prepared. To the macromonomer solution
was added the remaining methyl methacrylate. Next, in order, was
added optionally the IGI 1977 (wax) solution, the naphthoquinone
solution, the methacrylic acid, and the DMT (tertiary amine
accelerator). These sub-components were mixed at about 800 rpm for
10 min. Next, the Zealloy 1422 (nitrile rubber) was optionally
added while slowly increasing the mixing speed to about 900 rpm,
where the speed is held for about 15 minutes. The mixture was
allowed to sit for at least three hours, after which, the mixture
was mixed at about 1200 rpm for 20 minutes to create a uniform
consistency. Next the mixture was mixed at about 50 rpm while a
vacuum is applied to remove any entrapped air from the mixture.
[0199] These formulations were tested and would be expected to
exhibit an excellent balance of strength, elongation, stiffness,
and elastic recovery. In addition, the formulations would be
expected to show excellent properties even after long term aging at
elevated temperatures such as would be found in an automobile
either next to the engine or muffler or in a hot climate.
[0200] The composition for use as a structural adhesive, comprises
an elastomeric component comprising, the hybrid block copolymer,
optionally other elastomeric materials, also a methacrylate ester
monomer, optionally an acid monomer, optionally a phosphate ester,
optionally a cross-linked rubber, a tertiary amine initiator, an
inhibitor, and a thixotropic agent; and a catalyst component. The
hybrid polymer component is used at a level of 5-50% and most
preferably at a level of 5-20%.
Prophetic Example 15--Radiation Cured Adhesive
[0201] The macromonomer of Example 6 was used to prepare and test
radiation cured adhesives by the methods described in U.S. Pat. No.
4,556,464. 10-100 parts of the macromonomer of Example 6 were mixed
with 0-100 parts of a styrenic block copolymer, 25-300 parts of a
tackifying resin which was compatible with the hydrogenated
butadiene block of the hybrid block copolymer, for example Regalrez
1126 (a hydrogenated pure monomer resin with 72.degree. C. glass
transition available from Eastman) and with optionally 0-300 parts
of a plasticizer which was compatible with the hydrogenated
butadiene block of the hybrid block copolymer, for example Drakeol
7 (mineral oil from Penreco), and optionally with an initiator
which reacts with radiation to initiate the curing chemistry, for
example a UV photoinitiator Irgacure 651 (Ciba Geigy) and
optionally a crosslinking agent which can react in free radical
based curing such as a difunctional or multifunctional acrylate
like hexane diol diacrylate. The adhesives were prepared both by
blending in a sigma blade mixer and by solution blending in toluene
on a lab roller. They were cast onto Mylar, dried when cast from
solution, cured with UV light and tested for adhesive properties.
The adhesives are expected to show a good balance of tack and
elevated temperature cohesive strength such as shear strength.
Example 16--Printing Plate (Prophetic Example)
[0202] The printing plate formulations were prepared at a total of
20% wt solids in toluene and mixed in bottles (wrapped in foil to
prevent light exposure) on rollers. Solutions were poured into
Mylar boats and dried in a hood for 25 days. During drying the
films were covered to prevent light exposure. The 0.08 inch thick
films were dried, and then irradiated in a UVP CL1000 chamber with
5 eight watt 365 nm UVA bulbs for twenty minutes on each side. A
printing plate is made by solution casting from toluene a
formulation of 89% of the macromonomer of Example 6, 10% hexane
diol diacrylate, and 1% Irgacure 651. A second printing plate is
made like the first except the macromonomer is replaced by a 1:1
mixture of the macromonomer of Example 8 and Kraton D1161P (a
styrenic block copolymer with an isoprene midblock). A third
printing plate is made like the first except the macromonomer is
replaced by a 1:1 mixture of the macromonomer of Example 6 and
Kraton D1102K (a styrenic block copolymer with a butadiene
midblock). The printing plates comprising the hybrid block
copolymer are expected to exhibit improved resistance to ozone
compared to the printing plates of the prior art.
* * * * *